/[pcre]/code/trunk/doc/pcre.txt
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revision 578 by ph10, Wed Nov 17 17:55:57 2010 UTC revision 579 by ph10, Wed Nov 24 17:39:25 2010 UTC
# Line 2  Line 2 
2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. Neither has  synopses of each function in the library have not been included. Neither has
6  the pcredemo program. There are separate text files for the pcregrep and  the pcredemo program. There are separate text files for the pcregrep and
7  pcretest commands.  pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
# Line 269  REVISION Line 269  REVISION
269         Last updated: 13 November 2010         Last updated: 13 November 2010
270         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
271  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
272    
273    
274  PCREBUILD(3)                                                      PCREBUILD(3)  PCREBUILD(3)                                                      PCREBUILD(3)
275    
276    
# Line 600  REVISION Line 600  REVISION
600         Last updated: 29 September 2009         Last updated: 29 September 2009
601         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
602  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
603    
604    
605  PCREMATCHING(3)                                                PCREMATCHING(3)  PCREMATCHING(3)                                                PCREMATCHING(3)
606    
607    
# Line 804  REVISION Line 804  REVISION
804         Last updated: 17 November 2010         Last updated: 17 November 2010
805         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
806  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
807    
808    
809  PCREAPI(3)                                                          PCREAPI(3)  PCREAPI(3)                                                          PCREAPI(3)
810    
811    
# Line 1165  COMPILING A PATTERN Line 1165  COMPILING A PATTERN
1165         pcrepattern documentation). For those options that can be different  in         pcrepattern documentation). For those options that can be different  in
1166         different  parts  of  the pattern, the contents of the options argument         different  parts  of  the pattern, the contents of the options argument
1167         specifies their settings at the start of compilation and execution. The         specifies their settings at the start of compilation and execution. The
1168         PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at         PCRE_ANCHORED,  PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and
1169         the time of matching as well as at compile time.         PCRE_NO_START_OPT options can be set at the time of matching as well as
1170           at compile time.
1171    
1172         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1173         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1174         sets the variable pointed to by errptr to point to a textual error mes-         sets the variable pointed to by errptr to point to a textual error mes-
1175         sage. This is a static string that is part of the library. You must not         sage. This is a static string that is part of the library. You must not
1176         try to free it. The offset from the start of the pattern  to  the  byte         try  to  free  it. The offset from the start of the pattern to the byte
1177         that was being processed when the error was discovered is placed in the         that was being processed when the error was discovered is placed in the
1178         variable pointed to by erroffset, which must not be NULL. If it is,  an         variable  pointed to by erroffset, which must not be NULL. If it is, an
1179         immediate error is given. Some errors are not detected until checks are         immediate error is given. Some errors are not detected until checks are
1180         carried out when the whole pattern has been scanned; in this  case  the         carried  out  when the whole pattern has been scanned; in this case the
1181         offset is set to the end of the pattern.         offset is set to the end of the pattern.
1182    
1183         Note  that  the offset is in bytes, not characters, even in UTF-8 mode.         Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1184         It may point into the middle of a UTF-8 character  (for  example,  when         It  may  point  into the middle of a UTF-8 character (for example, when
1185         PCRE_ERROR_BADUTF8 is returned for an invalid UTF-8 string).         PCRE_ERROR_BADUTF8 is returned for an invalid UTF-8 string).
1186    
1187         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-
1188         codeptr argument is not NULL, a non-zero error code number is  returned         codeptr  argument is not NULL, a non-zero error code number is returned
1189         via  this argument in the event of an error. This is in addition to the         via this argument in the event of an error. This is in addition to  the
1190         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1191    
1192         If the final argument, tableptr, is NULL, PCRE uses a  default  set  of         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of
1193         character  tables  that  are  built  when  PCRE  is compiled, using the         character tables that are  built  when  PCRE  is  compiled,  using  the
1194         default C locale. Otherwise, tableptr must be an address  that  is  the         default  C  locale.  Otherwise, tableptr must be an address that is the
1195         result  of  a  call to pcre_maketables(). This value is stored with the         result of a call to pcre_maketables(). This value is  stored  with  the
1196         compiled pattern, and used again by pcre_exec(), unless  another  table         compiled  pattern,  and used again by pcre_exec(), unless another table
1197         pointer is passed to it. For more discussion, see the section on locale         pointer is passed to it. For more discussion, see the section on locale
1198         support below.         support below.
1199    
1200         This code fragment shows a typical straightforward  call  to  pcre_com-         This  code  fragment  shows a typical straightforward call to pcre_com-
1201         pile():         pile():
1202    
1203           pcre *re;           pcre *re;
# Line 1209  COMPILING A PATTERN Line 1210  COMPILING A PATTERN
1210             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1211             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1212    
1213         The  following  names  for option bits are defined in the pcre.h header         The following names for option bits are defined in  the  pcre.h  header
1214         file:         file:
1215    
1216           PCRE_ANCHORED           PCRE_ANCHORED
1217    
1218         If this bit is set, the pattern is forced to be "anchored", that is, it         If this bit is set, the pattern is forced to be "anchored", that is, it
1219         is  constrained to match only at the first matching point in the string         is constrained to match only at the first matching point in the  string
1220         that is being searched (the "subject string"). This effect can also  be         that  is being searched (the "subject string"). This effect can also be
1221         achieved  by appropriate constructs in the pattern itself, which is the         achieved by appropriate constructs in the pattern itself, which is  the
1222         only way to do it in Perl.         only way to do it in Perl.
1223    
1224           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1225    
1226         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1227         all  with  number  255, before each pattern item. For discussion of the         all with number 255, before each pattern item. For  discussion  of  the
1228         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1229    
1230           PCRE_BSR_ANYCRLF           PCRE_BSR_ANYCRLF
1231           PCRE_BSR_UNICODE           PCRE_BSR_UNICODE
1232    
1233         These options (which are mutually exclusive) control what the \R escape         These options (which are mutually exclusive) control what the \R escape
1234         sequence  matches.  The choice is either to match only CR, LF, or CRLF,         sequence matches. The choice is either to match only CR, LF,  or  CRLF,
1235         or to match any Unicode newline sequence. The default is specified when         or to match any Unicode newline sequence. The default is specified when
1236         PCRE is built. It can be overridden from within the pattern, or by set-         PCRE is built. It can be overridden from within the pattern, or by set-
1237         ting an option when a compiled pattern is matched.         ting an option when a compiled pattern is matched.
1238    
1239           PCRE_CASELESS           PCRE_CASELESS
1240    
1241         If this bit is set, letters in the pattern match both upper  and  lower         If  this  bit is set, letters in the pattern match both upper and lower
1242         case  letters.  It  is  equivalent  to  Perl's /i option, and it can be         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be
1243         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE
1244         always  understands the concept of case for characters whose values are         always understands the concept of case for characters whose values  are
1245         less than 128, so caseless matching is always possible. For  characters         less  than 128, so caseless matching is always possible. For characters
1246         with  higher  values,  the concept of case is supported if PCRE is com-         with higher values, the concept of case is supported if  PCRE  is  com-
1247         piled with Unicode property support, but not otherwise. If you want  to         piled  with Unicode property support, but not otherwise. If you want to
1248         use  caseless  matching  for  characters 128 and above, you must ensure         use caseless matching for characters 128 and  above,  you  must  ensure
1249         that PCRE is compiled with Unicode property support  as  well  as  with         that  PCRE  is  compiled  with Unicode property support as well as with
1250         UTF-8 support.         UTF-8 support.
1251    
1252           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1253    
1254         If  this bit is set, a dollar metacharacter in the pattern matches only         If this bit is set, a dollar metacharacter in the pattern matches  only
1255         at the end of the subject string. Without this option,  a  dollar  also         at  the  end  of the subject string. Without this option, a dollar also
1256         matches  immediately before a newline at the end of the string (but not         matches immediately before a newline at the end of the string (but  not
1257         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored
1258         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in         if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in
1259         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1260    
1261           PCRE_DOTALL           PCRE_DOTALL
1262    
1263         If this bit is set, a dot metacharacter in the pattern matches a  char-         If  this bit is set, a dot metacharacter in the pattern matches a char-
1264         acter of any value, including one that indicates a newline. However, it         acter of any value, including one that indicates a newline. However, it
1265         only ever matches one character, even if newlines are  coded  as  CRLF.         only  ever  matches  one character, even if newlines are coded as CRLF.
1266         Without  this option, a dot does not match when the current position is         Without this option, a dot does not match when the current position  is
1267         at a newline. This option is equivalent to Perl's /s option, and it can         at a newline. This option is equivalent to Perl's /s option, and it can
1268         be  changed within a pattern by a (?s) option setting. A negative class         be changed within a pattern by a (?s) option setting. A negative  class
1269         such as [^a] always matches newline characters, independent of the set-         such as [^a] always matches newline characters, independent of the set-
1270         ting of this option.         ting of this option.
1271    
1272           PCRE_DUPNAMES           PCRE_DUPNAMES
1273    
1274         If  this  bit is set, names used to identify capturing subpatterns need         If this bit is set, names used to identify capturing  subpatterns  need
1275         not be unique. This can be helpful for certain types of pattern when it         not be unique. This can be helpful for certain types of pattern when it
1276         is  known  that  only  one instance of the named subpattern can ever be         is known that only one instance of the named  subpattern  can  ever  be
1277         matched. There are more details of named subpatterns  below;  see  also         matched.  There  are  more details of named subpatterns below; see also
1278         the pcrepattern documentation.         the pcrepattern documentation.
1279    
1280           PCRE_EXTENDED           PCRE_EXTENDED
1281    
1282         If  this  bit  is  set,  whitespace  data characters in the pattern are         If this bit is set, whitespace  data  characters  in  the  pattern  are
1283         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1284         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1285         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1286         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x
1287         option, and it can be changed within a pattern by a  (?x)  option  set-         option,  and  it  can be changed within a pattern by a (?x) option set-
1288         ting.         ting.
1289    
1290         Which  characters  are  interpreted  as  newlines  is controlled by the         Which characters are interpreted  as  newlines  is  controlled  by  the
1291         options passed to pcre_compile() or by a special sequence at the  start         options  passed to pcre_compile() or by a special sequence at the start
1292         of  the  pattern, as described in the section entitled "Newline conven-         of the pattern, as described in the section entitled  "Newline  conven-
1293         tions" in the pcrepattern documentation. Note that the end of this type         tions" in the pcrepattern documentation. Note that the end of this type
1294         of  comment  is  a  literal  newline  sequence  in  the pattern; escape         of comment is  a  literal  newline  sequence  in  the  pattern;  escape
1295         sequences that happen to represent a newline do not count.         sequences that happen to represent a newline do not count.
1296    
1297         This option makes it possible to include  comments  inside  complicated         This  option  makes  it possible to include comments inside complicated
1298         patterns.   Note,  however,  that this applies only to data characters.         patterns.  Note, however, that this applies only  to  data  characters.
1299         Whitespace  characters  may  never  appear  within  special   character         Whitespace   characters  may  never  appear  within  special  character
1300         sequences in a pattern, for example within the sequence (?( that intro-         sequences in a pattern, for example within the sequence (?( that intro-
1301         duces a conditional subpattern.         duces a conditional subpattern.
1302    
1303           PCRE_EXTRA           PCRE_EXTRA
1304    
1305         This option was invented in order to turn on  additional  functionality         This  option  was invented in order to turn on additional functionality
1306         of  PCRE  that  is  incompatible with Perl, but it is currently of very         of PCRE that is incompatible with Perl, but it  is  currently  of  very
1307         little use. When set, any backslash in a pattern that is followed by  a         little  use. When set, any backslash in a pattern that is followed by a
1308         letter  that  has  no  special  meaning causes an error, thus reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1309         these combinations for future expansion. By  default,  as  in  Perl,  a         these  combinations  for  future  expansion.  By default, as in Perl, a
1310         backslash  followed by a letter with no special meaning is treated as a         backslash followed by a letter with no special meaning is treated as  a
1311         literal. (Perl can, however, be persuaded to give an error for this, by         literal. (Perl can, however, be persuaded to give an error for this, by
1312         running  it with the -w option.) There are at present no other features         running it with the -w option.) There are at present no other  features
1313         controlled by this option. It can also be set by a (?X) option  setting         controlled  by this option. It can also be set by a (?X) option setting
1314         within a pattern.         within a pattern.
1315    
1316           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1317    
1318         If  this  option  is  set,  an  unanchored pattern is required to match         If this option is set, an  unanchored  pattern  is  required  to  match
1319         before or at the first  newline  in  the  subject  string,  though  the         before  or  at  the  first  newline  in  the subject string, though the
1320         matched text may continue over the newline.         matched text may continue over the newline.
1321    
1322           PCRE_JAVASCRIPT_COMPAT           PCRE_JAVASCRIPT_COMPAT
1323    
1324         If this option is set, PCRE's behaviour is changed in some ways so that         If this option is set, PCRE's behaviour is changed in some ways so that
1325         it is compatible with JavaScript rather than Perl. The changes  are  as         it  is  compatible with JavaScript rather than Perl. The changes are as
1326         follows:         follows:
1327    
1328         (1)  A  lone  closing square bracket in a pattern causes a compile-time         (1) A lone closing square bracket in a pattern  causes  a  compile-time
1329         error, because this is illegal in JavaScript (by default it is  treated         error,  because this is illegal in JavaScript (by default it is treated
1330         as a data character). Thus, the pattern AB]CD becomes illegal when this         as a data character). Thus, the pattern AB]CD becomes illegal when this
1331         option is set.         option is set.
1332    
1333         (2) At run time, a back reference to an unset subpattern group  matches         (2)  At run time, a back reference to an unset subpattern group matches
1334         an  empty  string (by default this causes the current matching alterna-         an empty string (by default this causes the current  matching  alterna-
1335         tive to fail). A pattern such as (\1)(a) succeeds when this  option  is         tive  to  fail). A pattern such as (\1)(a) succeeds when this option is
1336         set  (assuming  it can find an "a" in the subject), whereas it fails by         set (assuming it can find an "a" in the subject), whereas it  fails  by
1337         default, for Perl compatibility.         default, for Perl compatibility.
1338    
1339           PCRE_MULTILINE           PCRE_MULTILINE
1340    
1341         By default, PCRE treats the subject string as consisting  of  a  single         By  default,  PCRE  treats the subject string as consisting of a single
1342         line  of characters (even if it actually contains newlines). The "start         line of characters (even if it actually contains newlines). The  "start
1343         of line" metacharacter (^) matches only at the  start  of  the  string,         of  line"  metacharacter  (^)  matches only at the start of the string,
1344         while  the  "end  of line" metacharacter ($) matches only at the end of         while the "end of line" metacharacter ($) matches only at  the  end  of
1345         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1346         is set). This is the same as Perl.         is set). This is the same as Perl.
1347    
1348         When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"
1349         constructs match immediately following or immediately  before  internal         constructs  match  immediately following or immediately before internal
1350         newlines  in  the  subject string, respectively, as well as at the very         newlines in the subject string, respectively, as well as  at  the  very
1351         start and end. This is equivalent to Perl's /m option, and  it  can  be         start  and  end.  This is equivalent to Perl's /m option, and it can be
1352         changed within a pattern by a (?m) option setting. If there are no new-         changed within a pattern by a (?m) option setting. If there are no new-
1353         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,         lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
1354         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1355    
1356           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1358  COMPILING A PATTERN Line 1359  COMPILING A PATTERN
1359           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1360           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1361    
1362         These  options  override the default newline definition that was chosen         These options override the default newline definition that  was  chosen
1363         when PCRE was built. Setting the first or the second specifies  that  a         when  PCRE  was built. Setting the first or the second specifies that a
1364         newline  is  indicated  by a single character (CR or LF, respectively).         newline is indicated by a single character (CR  or  LF,  respectively).
1365         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
1366         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1367         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1368         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1369         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1370         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1371         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS         U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
1372         (paragraph  separator,  U+2029).  The  last  two are recognized only in         (paragraph separator, U+2029). The last  two  are  recognized  only  in
1373         UTF-8 mode.         UTF-8 mode.
1374    
1375         The newline setting in the  options  word  uses  three  bits  that  are         The  newline  setting  in  the  options  word  uses three bits that are
1376         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
1377         used (default plus the five values above). This means that if  you  set         used  (default  plus the five values above). This means that if you set
1378         more  than one newline option, the combination may or may not be sensi-         more than one newline option, the combination may or may not be  sensi-
1379         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1380         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1381         cause an error.         cause an error.
1382    
1383         The only time that a line break in a pattern  is  specially  recognized         The  only  time  that a line break in a pattern is specially recognized
1384         when  compiling  is when PCRE_EXTENDED is set. CR and LF are whitespace         when compiling is when PCRE_EXTENDED is set. CR and LF  are  whitespace
1385         characters, and so are ignored in this mode. Also, an unescaped #  out-         characters,  and so are ignored in this mode. Also, an unescaped # out-
1386         side  a  character class indicates a comment that lasts until after the         side a character class indicates a comment that lasts until  after  the
1387         next line break sequence. In other circumstances, line break  sequences         next  line break sequence. In other circumstances, line break sequences
1388         in patterns are treated as literal data.         in patterns are treated as literal data.
1389    
1390         The newline option that is set at compile time becomes the default that         The newline option that is set at compile time becomes the default that
# Line 1392  COMPILING A PATTERN Line 1393  COMPILING A PATTERN
1393           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1394    
1395         If this option is set, it disables the use of numbered capturing paren-         If this option is set, it disables the use of numbered capturing paren-
1396         theses  in the pattern. Any opening parenthesis that is not followed by         theses in the pattern. Any opening parenthesis that is not followed  by
1397         ? behaves as if it were followed by ?: but named parentheses can  still         ?  behaves as if it were followed by ?: but named parentheses can still
1398         be  used  for  capturing  (and  they acquire numbers in the usual way).         be used for capturing (and they acquire  numbers  in  the  usual  way).
1399         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1400    
1401             NO_START_OPTIMIZE
1402    
1403           This  is an option that acts at matching time; that is, it is really an
1404           option for pcre_exec() or pcre_dfa_exec(). If  it  is  set  at  compile
1405           time,  it is remembered with the compiled pattern and assumed at match-
1406           ing time. For details  see  the  discussion  of  PCRE_NO_START_OPTIMIZE
1407           below.
1408    
1409           PCRE_UCP           PCRE_UCP
1410    
1411         This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,         This  option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W,
1412         \w,  and  some  of  the POSIX character classes. By default, only ASCII         \w, and some of the POSIX character classes.  By  default,  only  ASCII
1413         characters are recognized, but if PCRE_UCP is set,  Unicode  properties         characters  are  recognized, but if PCRE_UCP is set, Unicode properties
1414         are  used instead to classify characters. More details are given in the         are used instead to classify characters. More details are given in  the
1415         section on generic character types in the pcrepattern page. If you  set         section  on generic character types in the pcrepattern page. If you set
1416         PCRE_UCP,  matching  one of the items it affects takes much longer. The         PCRE_UCP, matching one of the items it affects takes much  longer.  The
1417         option is available only if PCRE has been compiled with  Unicode  prop-         option  is  available only if PCRE has been compiled with Unicode prop-
1418         erty support.         erty support.
1419    
1420           PCRE_UNGREEDY           PCRE_UNGREEDY
1421    
1422         This  option  inverts  the "greediness" of the quantifiers so that they         This option inverts the "greediness" of the quantifiers  so  that  they
1423         are not greedy by default, but become greedy if followed by "?". It  is         are  not greedy by default, but become greedy if followed by "?". It is
1424         not  compatible  with Perl. It can also be set by a (?U) option setting         not compatible with Perl. It can also be set by a (?U)  option  setting
1425         within the pattern.         within the pattern.
1426    
1427           PCRE_UTF8           PCRE_UTF8
1428    
1429         This option causes PCRE to regard both the pattern and the  subject  as         This  option  causes PCRE to regard both the pattern and the subject as
1430         strings  of  UTF-8 characters instead of single-byte character strings.         strings of UTF-8 characters instead of single-byte  character  strings.
1431         However, it is available only when PCRE is built to include UTF-8  sup-         However,  it is available only when PCRE is built to include UTF-8 sup-
1432         port.  If not, the use of this option provokes an error. Details of how         port. If not, the use of this option provokes an error. Details of  how
1433         this option changes the behaviour of PCRE are given in the  section  on         this  option  changes the behaviour of PCRE are given in the section on
1434         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1435    
1436           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1437    
1438         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
1439         automatically checked. There is a  discussion  about  the  validity  of         automatically  checked.  There  is  a  discussion about the validity of
1440         UTF-8  strings  in  the main pcre page. If an invalid UTF-8 sequence of         UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of
1441         bytes is found, pcre_compile() returns an error. If  you  already  know         bytes  is  found,  pcre_compile() returns an error. If you already know
1442         that your pattern is valid, and you want to skip this check for perfor-         that your pattern is valid, and you want to skip this check for perfor-
1443         mance reasons, you can set the PCRE_NO_UTF8_CHECK option.  When  it  is         mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is
1444         set,  the  effect  of  passing  an invalid UTF-8 string as a pattern is         set, the effect of passing an invalid UTF-8  string  as  a  pattern  is
1445         undefined. It may cause your program to crash. Note  that  this  option         undefined.  It  may  cause your program to crash. Note that this option
1446         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the
1447         UTF-8 validity checking of subject strings.         UTF-8 validity checking of subject strings.
1448    
1449    
1450  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1451    
1452         The following table lists the error  codes  than  may  be  returned  by         The  following  table  lists  the  error  codes than may be returned by
1453         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(), along with the error messages that may be returned  by
1454         both compiling functions. As PCRE has developed, some error codes  have         both  compiling functions. As PCRE has developed, some error codes have
1455         fallen out of use. To avoid confusion, they have not been re-used.         fallen out of use. To avoid confusion, they have not been re-used.
1456    
1457            0  no error            0  no error
# Line 1517  COMPILATION ERROR CODES Line 1526  COMPILATION ERROR CODES
1526           66  (*MARK) must have an argument           66  (*MARK) must have an argument
1527           67  this version of PCRE is not compiled with PCRE_UCP support           67  this version of PCRE is not compiled with PCRE_UCP support
1528    
1529         The  numbers  32  and 10000 in errors 48 and 49 are defaults; different         The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1530         values may be used if the limits were changed when PCRE was built.         values may be used if the limits were changed when PCRE was built.
1531    
1532    
# Line 1526  STUDYING A PATTERN Line 1535  STUDYING A PATTERN
1535         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1536              const char **errptr);              const char **errptr);
1537    
1538         If a compiled pattern is going to be used several times,  it  is  worth         If  a  compiled  pattern is going to be used several times, it is worth
1539         spending more time analyzing it in order to speed up the time taken for         spending more time analyzing it in order to speed up the time taken for
1540         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1541         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1542         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1543         pointer  to a pcre_extra block, in which the study_data field points to         pointer to a pcre_extra block, in which the study_data field points  to
1544         the results of the study.         the results of the study.
1545    
1546         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1547         pcre_exec()  or  pcre_dfa_exec(). However, a pcre_extra block also con-         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
1548         tains other fields that can be set by the caller before  the  block  is         tains  other  fields  that can be set by the caller before the block is
1549         passed; these are described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1550    
1551         If  studying  the  pattern  does  not  produce  any useful information,         If studying the  pattern  does  not  produce  any  useful  information,
1552         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1553         wants   to   pass   any   of   the   other  fields  to  pcre_exec()  or         wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or
1554         pcre_dfa_exec(), it must set up its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1555    
1556         The second argument of pcre_study() contains option bits.  At  present,         The  second  argument of pcre_study() contains option bits. At present,
1557         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1558    
1559         The  third argument for pcre_study() is a pointer for an error message.         The third argument for pcre_study() is a pointer for an error  message.
1560         If studying succeeds (even if no data is  returned),  the  variable  it         If  studying  succeeds  (even  if no data is returned), the variable it
1561         points  to  is  set  to NULL. Otherwise it is set to point to a textual         points to is set to NULL. Otherwise it is set to  point  to  a  textual
1562         error message. This is a static string that is part of the library. You         error message. This is a static string that is part of the library. You
1563         must  not  try  to  free it. You should test the error pointer for NULL         must not try to free it. You should test the  error  pointer  for  NULL
1564         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1565    
1566         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1565  STUDYING A PATTERN Line 1574  STUDYING A PATTERN
1574         Studying a pattern does two things: first, a lower bound for the length         Studying a pattern does two things: first, a lower bound for the length
1575         of subject string that is needed to match the pattern is computed. This         of subject string that is needed to match the pattern is computed. This
1576         does not mean that there are any strings of that length that match, but         does not mean that there are any strings of that length that match, but
1577         it  does  guarantee that no shorter strings match. The value is used by         it does guarantee that no shorter strings match. The value is  used  by
1578         pcre_exec() and pcre_dfa_exec() to avoid  wasting  time  by  trying  to         pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to
1579         match  strings  that are shorter than the lower bound. You can find out         match strings that are shorter than the lower bound. You can  find  out
1580         the value in a calling program via the pcre_fullinfo() function.         the value in a calling program via the pcre_fullinfo() function.
1581    
1582         Studying a pattern is also useful for non-anchored patterns that do not         Studying a pattern is also useful for non-anchored patterns that do not
1583         have  a  single fixed starting character. A bitmap of possible starting         have a single fixed starting character. A bitmap of  possible  starting
1584         bytes is created. This speeds up finding a position in the  subject  at         bytes  is  created. This speeds up finding a position in the subject at
1585         which to start matching.         which to start matching.
1586    
1587         The  two  optimizations  just  described can be disabled by setting the         The two optimizations just described can be  disabled  by  setting  the
1588         PCRE_NO_START_OPTIMIZE   option    when    calling    pcre_exec()    or         PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or
1589         pcre_dfa_exec().  You  might  want  to do this if your pattern contains         pcre_dfa_exec(). You might want to do this  if  your  pattern  contains
1590         callouts or (*MARK), and you want to make use of  these  facilities  in         callouts  or  (*MARK),  and you want to make use of these facilities in
1591         cases  where  matching fails. See the discussion of PCRE_NO_START_OPTI-         cases where matching fails. See the discussion  of  PCRE_NO_START_OPTI-
1592         MIZE below.         MIZE below.
1593    
1594    
1595  LOCALE SUPPORT  LOCALE SUPPORT
1596    
1597         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1598         letters,  digits, or whatever, by reference to a set of tables, indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1599         by character value. When running in UTF-8 mode, this  applies  only  to         by  character  value.  When running in UTF-8 mode, this applies only to
1600         characters  with  codes  less than 128. By default, higher-valued codes         characters with codes less than 128. By  default,  higher-valued  codes
1601         never match escapes such as \w or \d, but they can be tested with \p if         never match escapes such as \w or \d, but they can be tested with \p if
1602         PCRE  is  built with Unicode character property support. Alternatively,         PCRE is built with Unicode character property  support.  Alternatively,
1603         the PCRE_UCP option can be set at compile  time;  this  causes  \w  and         the  PCRE_UCP  option  can  be  set at compile time; this causes \w and
1604         friends to use Unicode property support instead of built-in tables. The         friends to use Unicode property support instead of built-in tables. The
1605         use of locales with Unicode is discouraged. If you are handling charac-         use of locales with Unicode is discouraged. If you are handling charac-
1606         ters  with codes greater than 128, you should either use UTF-8 and Uni-         ters with codes greater than 128, you should either use UTF-8 and  Uni-
1607         code, or use locales, but not try to mix the two.         code, or use locales, but not try to mix the two.
1608    
1609         PCRE contains an internal set of tables that are used  when  the  final         PCRE  contains  an  internal set of tables that are used when the final
1610         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1611         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1612         acters. However, when PCRE is built, it is possible to cause the inter-         acters. However, when PCRE is built, it is possible to cause the inter-
1613         nal tables to be rebuilt in the default "C" locale of the local system,         nal tables to be rebuilt in the default "C" locale of the local system,
1614         which may cause them to be different.         which may cause them to be different.
1615    
1616         The  internal tables can always be overridden by tables supplied by the         The internal tables can always be overridden by tables supplied by  the
1617         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1618         from  the  default.  As more and more applications change to using Uni-         from the default. As more and more applications change  to  using  Uni-
1619         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
1620    
1621         External tables are built by calling  the  pcre_maketables()  function,         External  tables  are  built by calling the pcre_maketables() function,
1622         which  has no arguments, in the relevant locale. The result can then be         which has no arguments, in the relevant locale. The result can then  be
1623         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1624         example,  to  build  and use tables that are appropriate for the French         example, to build and use tables that are appropriate  for  the  French
1625         locale (where accented characters with  values  greater  than  128  are         locale  (where  accented  characters  with  values greater than 128 are
1626         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1627    
1628           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1629           tables = pcre_maketables();           tables = pcre_maketables();
1630           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1631    
1632         The  locale  name "fr_FR" is used on Linux and other Unix-like systems;         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
1633         if you are using Windows, the name for the French locale is "french".         if you are using Windows, the name for the French locale is "french".
1634    
1635         When pcre_maketables() runs, the tables are built  in  memory  that  is         When  pcre_maketables()  runs,  the  tables are built in memory that is
1636         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1637         that the memory containing the tables remains available for as long  as         that  the memory containing the tables remains available for as long as
1638         it is needed.         it is needed.
1639    
1640         The pointer that is passed to pcre_compile() is saved with the compiled         The pointer that is passed to pcre_compile() is saved with the compiled
1641         pattern, and the same tables are used via this pointer by  pcre_study()         pattern,  and the same tables are used via this pointer by pcre_study()
1642         and normally also by pcre_exec(). Thus, by default, for any single pat-         and normally also by pcre_exec(). Thus, by default, for any single pat-
1643         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1644         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1645    
1646         It  is  possible to pass a table pointer or NULL (indicating the use of         It is possible to pass a table pointer or NULL (indicating the  use  of
1647         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1648         purpose,  this facility could be used to match a pattern in a different         purpose, this facility could be used to match a pattern in a  different
1649         locale from the one in which it was compiled. Passing table pointers at         locale from the one in which it was compiled. Passing table pointers at
1650         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1651    
# Line 1646  INFORMATION ABOUT A PATTERN Line 1655  INFORMATION ABOUT A PATTERN
1655         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1656              int what, void *where);              int what, void *where);
1657    
1658         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1659         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1660         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1661    
1662         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1663         pattern. The second argument is the result of pcre_study(), or NULL  if         pattern.  The second argument is the result of pcre_study(), or NULL if
1664         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1665         of information is required, and the fourth argument is a pointer  to  a         of  information  is required, and the fourth argument is a pointer to a
1666         variable  to  receive  the  data. The yield of the function is zero for         variable to receive the data. The yield of the  function  is  zero  for
1667         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1668    
1669           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1662  INFORMATION ABOUT A PATTERN Line 1671  INFORMATION ABOUT A PATTERN
1671           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1672           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1673    
1674         The "magic number" is placed at the start of each compiled  pattern  as         The  "magic  number" is placed at the start of each compiled pattern as
1675         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1676         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1677         pattern:         pattern:
1678    
1679           int rc;           int rc;
# Line 1675  INFORMATION ABOUT A PATTERN Line 1684  INFORMATION ABOUT A PATTERN
1684             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1685             &length);         /* where to put the data */             &length);         /* where to put the data */
1686    
1687         The  possible  values for the third argument are defined in pcre.h, and         The possible values for the third argument are defined in  pcre.h,  and
1688         are as follows:         are as follows:
1689    
1690           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1691    
1692         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1693         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1694         there are no back references.         there are no back references.
1695    
1696           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1697    
1698         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1699         argument should point to an int variable.         argument should point to an int variable.
1700    
1701           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1702    
1703         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1704         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1705         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1706         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1707         passing a NULL table pointer.         passing a NULL table pointer.
1708    
1709           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1710    
1711         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1712         non-anchored pattern. The fourth argument should point to an int  vari-         non-anchored  pattern. The fourth argument should point to an int vari-
1713         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
1714         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1715    
1716         If there is a fixed first byte, for example, from  a  pattern  such  as         If  there  is  a  fixed first byte, for example, from a pattern such as
1717         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1718    
1719         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1720         branch starts with "^", or         branch starts with "^", or
1721    
1722         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
1723         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1724    
1725         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1726         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1727         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1728    
1729           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1730    
1731         If  the pattern was studied, and this resulted in the construction of a         If the pattern was studied, and this resulted in the construction of  a
1732         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit table indicating a fixed set of bytes for the first byte in any
1733         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1734         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1735         able.         able.
1736    
1737           PCRE_INFO_HASCRORLF           PCRE_INFO_HASCRORLF
1738    
1739         Return  1  if  the  pattern  contains any explicit matches for CR or LF         Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1740         characters, otherwise 0. The fourth argument should  point  to  an  int         characters,  otherwise  0.  The  fourth argument should point to an int
1741         variable.  An explicit match is either a literal CR or LF character, or         variable. An explicit match is either a literal CR or LF character,  or
1742         \r or \n.         \r or \n.
1743    
1744           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1745    
1746         Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,         Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1747         otherwise  0. The fourth argument should point to an int variable. (?J)         otherwise 0. The fourth argument should point to an int variable.  (?J)
1748         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1749    
1750           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1751    
1752         Return the value of the rightmost literal byte that must exist  in  any         Return  the  value of the rightmost literal byte that must exist in any
1753         matched  string,  other  than  at  its  start,  if such a byte has been         matched string, other than at its  start,  if  such  a  byte  has  been
1754         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1755         is  no such byte, -1 is returned. For anchored patterns, a last literal         is no such byte, -1 is returned. For anchored patterns, a last  literal
1756         byte is recorded only if it follows something of variable  length.  For         byte  is  recorded only if it follows something of variable length. For
1757         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
1758         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1759    
1760           PCRE_INFO_MINLENGTH           PCRE_INFO_MINLENGTH
1761    
1762         If the pattern was studied and a minimum length  for  matching  subject         If  the  pattern  was studied and a minimum length for matching subject
1763         strings  was  computed,  its  value is returned. Otherwise the returned         strings was computed, its value is  returned.  Otherwise  the  returned
1764         value is -1. The value is a number of characters, not bytes  (this  may         value  is  -1. The value is a number of characters, not bytes (this may
1765         be  relevant in UTF-8 mode). The fourth argument should point to an int         be relevant in UTF-8 mode). The fourth argument should point to an  int
1766         variable. A non-negative value is a lower bound to the  length  of  any         variable.  A  non-negative  value is a lower bound to the length of any
1767         matching  string.  There  may not be any strings of that length that do         matching string. There may not be any strings of that  length  that  do
1768         actually match, but every string that does match is at least that long.         actually match, but every string that does match is at least that long.
1769    
1770           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1771           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1772           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1773    
1774         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE  supports the use of named as well as numbered capturing parenthe-
1775         ses.  The names are just an additional way of identifying the parenthe-         ses. The names are just an additional way of identifying the  parenthe-
1776         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
1777         pcre_get_named_substring()  are  provided  for extracting captured sub-         pcre_get_named_substring() are provided for  extracting  captured  sub-
1778         strings by name. It is also possible to extract the data  directly,  by         strings  by  name. It is also possible to extract the data directly, by
1779         first  converting  the  name to a number in order to access the correct         first converting the name to a number in order to  access  the  correct
1780         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
1781         the  conversion,  you  need  to  use  the  name-to-number map, which is         the conversion, you need  to  use  the  name-to-number  map,  which  is
1782         described by these three values.         described by these three values.
1783    
1784         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1785         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1786         of each entry; both of these  return  an  int  value.  The  entry  size         of  each  entry;  both  of  these  return  an int value. The entry size
1787         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
1788         a pointer to the first entry of the table  (a  pointer  to  char).  The         a  pointer  to  the  first  entry of the table (a pointer to char). The
1789         first two bytes of each entry are the number of the capturing parenthe-         first two bytes of each entry are the number of the capturing parenthe-
1790         sis, most significant byte first. The rest of the entry is  the  corre-         sis,  most  significant byte first. The rest of the entry is the corre-
1791         sponding name, zero terminated.         sponding name, zero terminated.
1792    
1793         The  names are in alphabetical order. Duplicate names may appear if (?|         The names are in alphabetical order. Duplicate names may appear if  (?|
1794         is used to create multiple groups with the same number, as described in         is used to create multiple groups with the same number, as described in
1795         the  section  on  duplicate subpattern numbers in the pcrepattern page.         the section on duplicate subpattern numbers in  the  pcrepattern  page.
1796         Duplicate names for subpatterns with different  numbers  are  permitted         Duplicate  names  for  subpatterns with different numbers are permitted
1797         only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they         only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they
1798         appear in the table in the order in which they were found in  the  pat-         appear  in  the table in the order in which they were found in the pat-
1799         tern.  In  the  absence  of (?| this is the order of increasing number;         tern. In the absence of (?| this is the  order  of  increasing  number;
1800         when (?| is used this is not necessarily the case because later subpat-         when (?| is used this is not necessarily the case because later subpat-
1801         terns may have lower numbers.         terns may have lower numbers.
1802    
1803         As  a  simple  example of the name/number table, consider the following         As a simple example of the name/number table,  consider  the  following
1804         pattern (assume PCRE_EXTENDED is set, so white space -  including  new-         pattern  (assume  PCRE_EXTENDED is set, so white space - including new-
1805         lines - is ignored):         lines - is ignored):
1806    
1807           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1808           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1809    
1810         There  are  four  named subpatterns, so the table has four entries, and         There are four named subpatterns, so the table has  four  entries,  and
1811         each entry in the table is eight bytes long. The table is  as  follows,         each  entry  in the table is eight bytes long. The table is as follows,
1812         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1813         as ??:         as ??:
1814    
# Line 1808  INFORMATION ABOUT A PATTERN Line 1817  INFORMATION ABOUT A PATTERN
1817           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1818           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1819    
1820         When writing code to extract data  from  named  subpatterns  using  the         When  writing  code  to  extract  data from named subpatterns using the
1821         name-to-number  map,  remember that the length of the entries is likely         name-to-number map, remember that the length of the entries  is  likely
1822         to be different for each compiled pattern.         to be different for each compiled pattern.
1823    
1824           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1825    
1826         Return 1  if  the  pattern  can  be  used  for  partial  matching  with         Return  1  if  the  pattern  can  be  used  for  partial  matching with
1827         pcre_exec(),  otherwise  0.  The fourth argument should point to an int         pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1828         variable. From  release  8.00,  this  always  returns  1,  because  the         variable.  From  release  8.00,  this  always  returns  1,  because the
1829         restrictions  that  previously  applied  to  partial matching have been         restrictions that previously applied  to  partial  matching  have  been
1830         lifted. The pcrepartial documentation gives details of  partial  match-         lifted.  The  pcrepartial documentation gives details of partial match-
1831         ing.         ing.
1832    
1833           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1834    
1835         Return  a  copy of the options with which the pattern was compiled. The         Return a copy of the options with which the pattern was  compiled.  The
1836         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1837         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1838         by any top-level option settings at the start of the pattern itself. In         by any top-level option settings at the start of the pattern itself. In
1839         other  words,  they are the options that will be in force when matching         other words, they are the options that will be in force  when  matching
1840         starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with         starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1841         the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,         the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1842         and PCRE_EXTENDED.         and PCRE_EXTENDED.
1843    
1844         A pattern is automatically anchored by PCRE if  all  of  its  top-level         A  pattern  is  automatically  anchored by PCRE if all of its top-level
1845         alternatives begin with one of the following:         alternatives begin with one of the following:
1846    
1847           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1846  INFORMATION ABOUT A PATTERN Line 1855  INFORMATION ABOUT A PATTERN
1855    
1856           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1857    
1858         Return the size of the compiled pattern, that is, the  value  that  was         Return  the  size  of the compiled pattern, that is, the value that was
1859         passed as the argument to pcre_malloc() when PCRE was getting memory in         passed as the argument to pcre_malloc() when PCRE was getting memory in
1860         which to place the compiled data. The fourth argument should point to a         which to place the compiled data. The fourth argument should point to a
1861         size_t variable.         size_t variable.
# Line 1854  INFORMATION ABOUT A PATTERN Line 1863  INFORMATION ABOUT A PATTERN
1863           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1864    
1865         Return the size of the data block pointed to by the study_data field in         Return the size of the data block pointed to by the study_data field in
1866         a pcre_extra block. That is,  it  is  the  value  that  was  passed  to         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to
1867         pcre_malloc() when PCRE was getting memory into which to place the data         pcre_malloc() when PCRE was getting memory into which to place the data
1868         created by pcre_study(). If pcre_extra is NULL, or there  is  no  study         created  by  pcre_study().  If pcre_extra is NULL, or there is no study
1869         data,  zero  is  returned. The fourth argument should point to a size_t         data, zero is returned. The fourth argument should point  to  a  size_t
1870         variable.         variable.
1871    
1872    
# Line 1865  OBSOLETE INFO FUNCTION Line 1874  OBSOLETE INFO FUNCTION
1874    
1875         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1876    
1877         The pcre_info() function is now obsolete because its interface  is  too         The  pcre_info()  function is now obsolete because its interface is too
1878         restrictive  to return all the available data about a compiled pattern.         restrictive to return all the available data about a compiled  pattern.
1879         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
1880         pcre_info()  is the number of capturing subpatterns, or one of the fol-         pcre_info() is the number of capturing subpatterns, or one of the  fol-
1881         lowing negative numbers:         lowing negative numbers:
1882    
1883           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1884           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1885    
1886         If the optptr argument is not NULL, a copy of the  options  with  which         If  the  optptr  argument is not NULL, a copy of the options with which
1887         the  pattern  was  compiled  is placed in the integer it points to (see         the pattern was compiled is placed in the integer  it  points  to  (see
1888         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1889    
1890         If the pattern is not anchored and the  firstcharptr  argument  is  not         If  the  pattern  is  not anchored and the firstcharptr argument is not
1891         NULL,  it is used to pass back information about the first character of         NULL, it is used to pass back information about the first character  of
1892         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1893    
1894    
# Line 1887  REFERENCE COUNTS Line 1896  REFERENCE COUNTS
1896    
1897         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1898    
1899         The pcre_refcount() function is used to maintain a reference  count  in         The  pcre_refcount()  function is used to maintain a reference count in
1900         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
1901         benefit of applications that  operate  in  an  object-oriented  manner,         benefit  of  applications  that  operate  in an object-oriented manner,
1902         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1903         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
1904    
1905         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1906         zero.   It is changed only by calling this function, whose action is to         zero.  It is changed only by calling this function, whose action is  to
1907         add the adjust value (which may be positive or  negative)  to  it.  The         add  the  adjust  value  (which may be positive or negative) to it. The
1908         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
1909         is constrained to lie between 0 and 65535, inclusive. If the new  value         is  constrained to lie between 0 and 65535, inclusive. If the new value
1910         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1911    
1912         Except  when it is zero, the reference count is not correctly preserved         Except when it is zero, the reference count is not correctly  preserved
1913         if a pattern is compiled on one host and then  transferred  to  a  host         if  a  pattern  is  compiled on one host and then transferred to a host
1914         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1915    
1916    
# Line 1911  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1920  MATCHING A PATTERN: THE TRADITIONAL FUNC
1920              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1921              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1922    
1923         The  function pcre_exec() is called to match a subject string against a         The function pcre_exec() is called to match a subject string against  a
1924         compiled pattern, which is passed in the code argument. If the  pattern         compiled  pattern, which is passed in the code argument. If the pattern
1925         was  studied,  the  result  of  the study should be passed in the extra         was studied, the result of the study should  be  passed  in  the  extra
1926         argument. This function is the main matching facility of  the  library,         argument.  This  function is the main matching facility of the library,
1927         and it operates in a Perl-like manner. For specialist use there is also         and it operates in a Perl-like manner. For specialist use there is also
1928         an alternative matching function, which is described below in the  sec-         an  alternative matching function, which is described below in the sec-
1929         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1930    
1931         In  most applications, the pattern will have been compiled (and option-         In most applications, the pattern will have been compiled (and  option-
1932         ally studied) in the same process that calls pcre_exec().  However,  it         ally  studied)  in the same process that calls pcre_exec(). However, it
1933         is possible to save compiled patterns and study data, and then use them         is possible to save compiled patterns and study data, and then use them
1934         later in different processes, possibly even on different hosts.  For  a         later  in  different processes, possibly even on different hosts. For a
1935         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1936    
1937         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1941  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1950  MATCHING A PATTERN: THE TRADITIONAL FUNC
1950    
1951     Extra data for pcre_exec()     Extra data for pcre_exec()
1952    
1953         If  the  extra argument is not NULL, it must point to a pcre_extra data         If the extra argument is not NULL, it must point to a  pcre_extra  data
1954         block. The pcre_study() function returns such a block (when it  doesn't         block.  The pcre_study() function returns such a block (when it doesn't
1955         return  NULL), but you can also create one for yourself, and pass addi-         return NULL), but you can also create one for yourself, and pass  addi-
1956         tional information in it. The pcre_extra block contains  the  following         tional  information  in it. The pcre_extra block contains the following
1957         fields (not necessarily in this order):         fields (not necessarily in this order):
1958    
1959           unsigned long int flags;           unsigned long int flags;
# Line 1955  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1964  MATCHING A PATTERN: THE TRADITIONAL FUNC
1964           const unsigned char *tables;           const unsigned char *tables;
1965           unsigned char **mark;           unsigned char **mark;
1966    
1967         The  flags  field  is a bitmap that specifies which of the other fields         The flags field is a bitmap that specifies which of  the  other  fields
1968         are set. The flag bits are:         are set. The flag bits are:
1969    
1970           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1965  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1974  MATCHING A PATTERN: THE TRADITIONAL FUNC
1974           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1975           PCRE_EXTRA_MARK           PCRE_EXTRA_MARK
1976    
1977         Other flag bits should be set to zero. The study_data field is  set  in         Other  flag  bits should be set to zero. The study_data field is set in
1978         the  pcre_extra  block  that is returned by pcre_study(), together with         the pcre_extra block that is returned by  pcre_study(),  together  with
1979         the appropriate flag bit. You should not set this yourself, but you may         the appropriate flag bit. You should not set this yourself, but you may
1980         add  to  the  block by setting the other fields and their corresponding         add to the block by setting the other fields  and  their  corresponding
1981         flag bits.         flag bits.
1982    
1983         The match_limit field provides a means of preventing PCRE from using up         The match_limit field provides a means of preventing PCRE from using up
1984         a  vast amount of resources when running patterns that are not going to         a vast amount of resources when running patterns that are not going  to
1985         match, but which have a very large number  of  possibilities  in  their         match,  but  which  have  a very large number of possibilities in their
1986         search  trees. The classic example is a pattern that uses nested unlim-         search trees. The classic example is a pattern that uses nested  unlim-
1987         ited repeats.         ited repeats.
1988    
1989         Internally, PCRE uses a function called match() which it calls  repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1990         edly  (sometimes  recursively). The limit set by match_limit is imposed         edly (sometimes recursively). The limit set by match_limit  is  imposed
1991         on the number of times this function is called during  a  match,  which         on  the  number  of times this function is called during a match, which
1992         has  the  effect  of  limiting the amount of backtracking that can take         has the effect of limiting the amount of  backtracking  that  can  take
1993         place. For patterns that are not anchored, the count restarts from zero         place. For patterns that are not anchored, the count restarts from zero
1994         for each position in the subject string.         for each position in the subject string.
1995    
1996         The  default  value  for  the  limit can be set when PCRE is built; the         The default value for the limit can be set  when  PCRE  is  built;  the
1997         default default is 10 million, which handles all but the  most  extreme         default  default  is 10 million, which handles all but the most extreme
1998         cases.  You  can  override  the  default by suppling pcre_exec() with a         cases. You can override the default  by  suppling  pcre_exec()  with  a
1999         pcre_extra    block    in    which    match_limit    is    set,     and         pcre_extra     block    in    which    match_limit    is    set,    and
2000         PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is
2001         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
2002    
2003         The match_limit_recursion field is similar to match_limit, but  instead         The  match_limit_recursion field is similar to match_limit, but instead
2004         of limiting the total number of times that match() is called, it limits         of limiting the total number of times that match() is called, it limits
2005         the depth of recursion. The recursion depth is a  smaller  number  than         the  depth  of  recursion. The recursion depth is a smaller number than
2006         the  total number of calls, because not all calls to match() are recur-         the total number of calls, because not all calls to match() are  recur-
2007         sive.  This limit is of use only if it is set smaller than match_limit.         sive.  This limit is of use only if it is set smaller than match_limit.
2008    
2009         Limiting the recursion depth limits the amount of  stack  that  can  be         Limiting  the  recursion  depth  limits the amount of stack that can be
2010         used, or, when PCRE has been compiled to use memory on the heap instead         used, or, when PCRE has been compiled to use memory on the heap instead
2011         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
2012    
2013         The default value for match_limit_recursion can be  set  when  PCRE  is         The  default  value  for  match_limit_recursion can be set when PCRE is
2014         built;  the  default  default  is  the  same  value  as the default for         built; the default default  is  the  same  value  as  the  default  for
2015         match_limit. You can override the default by suppling pcre_exec()  with         match_limit.  You can override the default by suppling pcre_exec() with
2016         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
2017         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
2018         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2019    
2020         The  callout_data  field is used in conjunction with the "callout" fea-         The callout_data field is used in conjunction with the  "callout"  fea-
2021         ture, and is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
2022    
2023         The tables field  is  used  to  pass  a  character  tables  pointer  to         The  tables  field  is  used  to  pass  a  character  tables pointer to
2024         pcre_exec();  this overrides the value that is stored with the compiled         pcre_exec(); this overrides the value that is stored with the  compiled
2025         pattern. A non-NULL value is stored with the compiled pattern  only  if         pattern.  A  non-NULL value is stored with the compiled pattern only if
2026         custom  tables  were  supplied to pcre_compile() via its tableptr argu-         custom tables were supplied to pcre_compile() via  its  tableptr  argu-
2027         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
2028         PCRE's  internal  tables  to be used. This facility is helpful when re-         PCRE's internal tables to be used. This facility is  helpful  when  re-
2029         using patterns that have been saved after compiling  with  an  external         using  patterns  that  have been saved after compiling with an external
2030         set  of  tables,  because  the  external tables might be at a different         set of tables, because the external tables  might  be  at  a  different
2031         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address  when  pcre_exec() is called. See the pcreprecompile documenta-
2032         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2033    
2034         If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be         If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
2035         set to point to a char * variable. If the pattern  contains  any  back-         set  to  point  to a char * variable. If the pattern contains any back-
2036         tracking  control verbs such as (*MARK:NAME), and the execution ends up         tracking control verbs such as (*MARK:NAME), and the execution ends  up
2037         with a name to pass back, a pointer to the  name  string  (zero  termi-         with  a  name  to  pass back, a pointer to the name string (zero termi-
2038         nated)  is  placed  in  the  variable pointed to by the mark field. The         nated) is placed in the variable pointed to  by  the  mark  field.  The
2039         names are within the compiled pattern; if you wish  to  retain  such  a         names  are  within  the  compiled pattern; if you wish to retain such a
2040         name  you must copy it before freeing the memory of a compiled pattern.         name you must copy it before freeing the memory of a compiled  pattern.
2041         If there is no name to pass back, the variable pointed to by  the  mark         If  there  is no name to pass back, the variable pointed to by the mark
2042         field  set  to NULL. For details of the backtracking control verbs, see         field set to NULL. For details of the backtracking control  verbs,  see
2043         the section entitled "Backtracking control" in the pcrepattern documen-         the section entitled "Backtracking control" in the pcrepattern documen-
2044         tation.         tation.
2045    
2046     Option bits for pcre_exec()     Option bits for pcre_exec()
2047    
2048         The  unused  bits of the options argument for pcre_exec() must be zero.         The unused bits of the options argument for pcre_exec() must  be  zero.
2049         The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
2050         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,         PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,
2051         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and         PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,  and
2052         PCRE_PARTIAL_HARD.         PCRE_PARTIAL_HARD.
2053    
2054           PCRE_ANCHORED           PCRE_ANCHORED
2055    
2056         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
2057         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
2058         turned  out to be anchored by virtue of its contents, it cannot be made         turned out to be anchored by virtue of its contents, it cannot be  made
2059         unachored at matching time.         unachored at matching time.
2060    
2061           PCRE_BSR_ANYCRLF           PCRE_BSR_ANYCRLF
2062           PCRE_BSR_UNICODE           PCRE_BSR_UNICODE
2063    
2064         These options (which are mutually exclusive) control what the \R escape         These options (which are mutually exclusive) control what the \R escape
2065         sequence  matches.  The choice is either to match only CR, LF, or CRLF,         sequence matches. The choice is either to match only CR, LF,  or  CRLF,
2066         or to match any Unicode newline sequence. These  options  override  the         or  to  match  any Unicode newline sequence. These options override the
2067         choice that was made or defaulted when the pattern was compiled.         choice that was made or defaulted when the pattern was compiled.
2068    
2069           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 2063  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2072  MATCHING A PATTERN: THE TRADITIONAL FUNC
2072           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
2073           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
2074    
2075         These  options  override  the  newline  definition  that  was chosen or         These options override  the  newline  definition  that  was  chosen  or
2076         defaulted when the pattern was compiled. For details, see the  descrip-         defaulted  when the pattern was compiled. For details, see the descrip-
2077         tion  of  pcre_compile()  above.  During  matching,  the newline choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
2078         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
2079         ters.  It may also alter the way the match position is advanced after a         ters. It may also alter the way the match position is advanced after  a
2080         match failure for an unanchored pattern.         match failure for an unanchored pattern.
2081    
2082         When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is         When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
2083         set,  and a match attempt for an unanchored pattern fails when the cur-         set, and a match attempt for an unanchored pattern fails when the  cur-
2084         rent position is at a  CRLF  sequence,  and  the  pattern  contains  no         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
2085         explicit  matches  for  CR  or  LF  characters,  the  match position is         explicit matches for  CR  or  LF  characters,  the  match  position  is
2086         advanced by two characters instead of one, in other words, to after the         advanced by two characters instead of one, in other words, to after the
2087         CRLF.         CRLF.
2088    
2089         The above rule is a compromise that makes the most common cases work as         The above rule is a compromise that makes the most common cases work as
2090         expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL         expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
2091         option is not set), it does not match the string "\r\nA" because, after         option is not set), it does not match the string "\r\nA" because, after
2092         failing at the start, it skips both the CR and the LF before  retrying.         failing  at the start, it skips both the CR and the LF before retrying.
2093         However,  the  pattern  [\r\n]A does match that string, because it con-         However, the pattern [\r\n]A does match that string,  because  it  con-
2094         tains an explicit CR or LF reference, and so advances only by one char-         tains an explicit CR or LF reference, and so advances only by one char-
2095         acter after the first failure.         acter after the first failure.
2096    
2097         An explicit match for CR of LF is either a literal appearance of one of         An explicit match for CR of LF is either a literal appearance of one of
2098         those characters, or one of the \r or  \n  escape  sequences.  Implicit         those  characters,  or  one  of the \r or \n escape sequences. Implicit
2099         matches  such  as [^X] do not count, nor does \s (which includes CR and         matches such as [^X] do not count, nor does \s (which includes  CR  and
2100         LF in the characters that it matches).         LF in the characters that it matches).
2101    
2102         Notwithstanding the above, anomalous effects may still occur when  CRLF         Notwithstanding  the above, anomalous effects may still occur when CRLF
2103         is a valid newline sequence and explicit \r or \n escapes appear in the         is a valid newline sequence and explicit \r or \n escapes appear in the
2104         pattern.         pattern.
2105    
2106           PCRE_NOTBOL           PCRE_NOTBOL
2107    
2108         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2109         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
2110         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
2111         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
2112         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2113    
2114           PCRE_NOTEOL           PCRE_NOTEOL
2115    
2116         This option specifies that the end of the subject string is not the end         This option specifies that the end of the subject string is not the end
2117         of  a line, so the dollar metacharacter should not match it nor (except         of a line, so the dollar metacharacter should not match it nor  (except
2118         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
2119         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2120         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
2121         not affect \Z or \z.         not affect \Z or \z.
2122    
2123           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2124    
2125         An empty string is not considered to be a valid match if this option is         An empty string is not considered to be a valid match if this option is
2126         set. If there are alternatives in the pattern, they are tried.  If  all         set.  If  there are alternatives in the pattern, they are tried. If all
2127         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
2128         example, if the pattern         example, if the pattern
2129    
2130           a?b?           a?b?
2131    
2132         is applied to a string not beginning with "a" or  "b",  it  matches  an         is  applied  to  a  string not beginning with "a" or "b", it matches an
2133         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this         empty string at the start of the subject. With PCRE_NOTEMPTY set,  this
2134         match is not valid, so PCRE searches further into the string for occur-         match is not valid, so PCRE searches further into the string for occur-
2135         rences of "a" or "b".         rences of "a" or "b".
2136    
2137           PCRE_NOTEMPTY_ATSTART           PCRE_NOTEMPTY_ATSTART
2138    
2139         This  is  like PCRE_NOTEMPTY, except that an empty string match that is         This is like PCRE_NOTEMPTY, except that an empty string match  that  is
2140         not at the start of  the  subject  is  permitted.  If  the  pattern  is         not  at  the  start  of  the  subject  is  permitted. If the pattern is
2141         anchored, such a match can occur only if the pattern contains \K.         anchored, such a match can occur only if the pattern contains \K.
2142    
2143         Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or
2144         PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern         PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern
2145         match  of  the empty string within its split() function, and when using         match of the empty string within its split() function, and  when  using
2146         the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after         the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after
2147         matching a null string by first trying the match again at the same off-         matching a null string by first trying the match again at the same off-
2148         set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that         set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2149         fails, by advancing the starting offset (see below) and trying an ordi-         fails, by advancing the starting offset (see below) and trying an ordi-
2150         nary match again. There is some code that demonstrates how to  do  this         nary  match  again. There is some code that demonstrates how to do this
2151         in  the  pcredemo sample program. In the most general case, you have to         in the pcredemo sample program. In the most general case, you  have  to
2152         check to see if the newline convention recognizes CRLF  as  a  newline,         check  to  see  if the newline convention recognizes CRLF as a newline,
2153         and  if so, and the current character is CR followed by LF, advance the         and if so, and the current character is CR followed by LF, advance  the
2154         starting offset by two characters instead of one.         starting offset by two characters instead of one.
2155    
2156           PCRE_NO_START_OPTIMIZE           PCRE_NO_START_OPTIMIZE
2157    
2158         There are a number of optimizations that pcre_exec() uses at the  start         There  are a number of optimizations that pcre_exec() uses at the start
2159         of  a  match,  in  order to speed up the process. For example, if it is         of a match, in order to speed up the process. For  example,  if  it  is
2160         known that an unanchored match must start with a specific character, it         known that an unanchored match must start with a specific character, it
2161         searches  the  subject  for that character, and fails immediately if it         searches the subject for that character, and fails  immediately  if  it
2162         cannot find it, without actually running the  main  matching  function.         cannot  find  it,  without actually running the main matching function.
2163         This means that a special item such as (*COMMIT) at the start of a pat-         This means that a special item such as (*COMMIT) at the start of a pat-
2164         tern is not considered until after a suitable starting  point  for  the         tern  is  not  considered until after a suitable starting point for the
2165         match  has been found. When callouts or (*MARK) items are in use, these         match has been found. When callouts or (*MARK) items are in use,  these
2166         "start-up" optimizations can cause them to be skipped if the pattern is         "start-up" optimizations can cause them to be skipped if the pattern is
2167         never  actually  used.  The start-up optimizations are in effect a pre-         never actually used. The start-up optimizations are in  effect  a  pre-
2168         scan of the subject that takes place before the pattern is run.         scan of the subject that takes place before the pattern is run.
2169    
2170         The PCRE_NO_START_OPTIMIZE option disables the start-up  optimizations,         The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
2171         possibly  causing  performance  to  suffer,  but ensuring that in cases         possibly causing performance to suffer,  but  ensuring  that  in  cases
2172         where the result is "no match", the callouts do occur, and  that  items         where  the  result is "no match", the callouts do occur, and that items
2173         such as (*COMMIT) and (*MARK) are considered at every possible starting         such as (*COMMIT) and (*MARK) are considered at every possible starting
2174         position in the subject  string.   Setting  PCRE_NO_START_OPTIMIZE  can         position  in  the  subject  string. If PCRE_NO_START_OPTIMIZE is set at
2175         change the outcome of a matching operation.  Consider the pattern         compile time, it cannot be unset at matching time.
2176    
2177           Setting PCRE_NO_START_OPTIMIZE can change the  outcome  of  a  matching
2178           operation.  Consider the pattern
2179    
2180           (*COMMIT)ABC           (*COMMIT)ABC
2181    
# Line 2862  AUTHOR Line 2874  AUTHOR
2874    
2875  REVISION  REVISION
2876    
2877         Last updated: 13 November 2010         Last updated: 21 November 2010
2878         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
2879  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2880    
2881    
2882  PCRECALLOUT(3)                                                  PCRECALLOUT(3)  PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2883    
2884    
# Line 2930  MISSING CALLOUTS Line 2942  MISSING CALLOUTS
2942         patterns, if it has been scanned far enough.         patterns, if it has been scanned far enough.
2943    
2944         You  can disable these optimizations by passing the PCRE_NO_START_OPTI-         You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
2945         MIZE option to pcre_exec() or  pcre_dfa_exec().  This  slows  down  the         MIZE option to pcre_compile(), pcre_exec(), or pcre_dfa_exec(),  or  by
2946         matching  process,  but  does  ensure that callouts such as the example         starting the pattern with (*NO_START_OPT). This slows down the matching
2947         above are obeyed.         process, but does ensure that callouts such as the  example  above  are
2948           obeyed.
2949    
2950    
2951  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2952    
2953         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
2954         tion  defined by pcre_callout is called (if it is set). This applies to         tion defined by pcre_callout is called (if it is set). This applies  to
2955         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
2956         only  argument  to  the callout function is a pointer to a pcre_callout         only argument to the callout function is a pointer  to  a  pcre_callout
2957         block. This structure contains the following fields:         block. This structure contains the following fields:
2958    
2959           int          version;           int          version;
# Line 2956  THE CALLOUT INTERFACE Line 2969  THE CALLOUT INTERFACE
2969           int          pattern_position;           int          pattern_position;
2970           int          next_item_length;           int          next_item_length;
2971    
2972         The version field is an integer containing the version  number  of  the         The  version  field  is an integer containing the version number of the
2973         block  format. The initial version was 0; the current version is 1. The         block format. The initial version was 0; the current version is 1.  The
2974         version number will change again in future  if  additional  fields  are         version  number  will  change  again in future if additional fields are
2975         added, but the intention is never to remove any of the existing fields.         added, but the intention is never to remove any of the existing fields.
2976    
2977         The  callout_number  field  contains the number of the callout, as com-         The callout_number field contains the number of the  callout,  as  com-
2978         piled into the pattern (that is, the number after ?C for  manual  call-         piled  into  the pattern (that is, the number after ?C for manual call-
2979         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
2980    
2981         The  offset_vector field is a pointer to the vector of offsets that was         The offset_vector field is a pointer to the vector of offsets that  was
2982         passed  by  the  caller  to  pcre_exec()   or   pcre_dfa_exec().   When         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When
2983         pcre_exec()  is used, the contents can be inspected in order to extract         pcre_exec() is used, the contents can be inspected in order to  extract
2984         substrings that have been matched so  far,  in  the  same  way  as  for         substrings  that  have  been  matched  so  far,  in the same way as for
2985         extracting  substrings after a match has completed. For pcre_dfa_exec()         extracting substrings after a match has completed. For  pcre_dfa_exec()
2986         this field is not useful.         this field is not useful.
2987    
2988         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2989         were passed to pcre_exec().         were passed to pcre_exec().
2990    
2991         The  start_match  field normally contains the offset within the subject         The start_match field normally contains the offset within  the  subject
2992         at which the current match attempt  started.  However,  if  the  escape         at  which  the  current  match  attempt started. However, if the escape
2993         sequence  \K has been encountered, this value is changed to reflect the         sequence \K has been encountered, this value is changed to reflect  the
2994         modified starting point. If the pattern is not  anchored,  the  callout         modified  starting  point.  If the pattern is not anchored, the callout
2995         function may be called several times from the same point in the pattern         function may be called several times from the same point in the pattern
2996         for different starting points in the subject.         for different starting points in the subject.
2997    
2998         The current_position field contains the offset within  the  subject  of         The  current_position  field  contains the offset within the subject of
2999         the current match pointer.         the current match pointer.
3000    
3001         When  the  pcre_exec() function is used, the capture_top field contains         When the pcre_exec() function is used, the capture_top  field  contains
3002         one more than the number of the highest numbered captured substring  so         one  more than the number of the highest numbered captured substring so
3003         far.  If  no substrings have been captured, the value of capture_top is         far. If no substrings have been captured, the value of  capture_top  is
3004         one. This is always the case when pcre_dfa_exec() is used,  because  it         one.  This  is always the case when pcre_dfa_exec() is used, because it
3005         does not support captured substrings.         does not support captured substrings.
3006    
3007         The  capture_last  field  contains the number of the most recently cap-         The capture_last field contains the number of the  most  recently  cap-
3008         tured substring. If no substrings have been captured, its value is  -1.         tured  substring. If no substrings have been captured, its value is -1.
3009         This is always the case when pcre_dfa_exec() is used.         This is always the case when pcre_dfa_exec() is used.
3010    
3011         The  callout_data  field contains a value that is passed to pcre_exec()         The callout_data field contains a value that is passed  to  pcre_exec()
3012         or pcre_dfa_exec() specifically so that it can be passed back in  call-         or  pcre_dfa_exec() specifically so that it can be passed back in call-
3013         outs.  It  is  passed  in the pcre_callout field of the pcre_extra data         outs. It is passed in the pcre_callout field  of  the  pcre_extra  data
3014         structure. If no such data was passed, the value of callout_data  in  a         structure.  If  no such data was passed, the value of callout_data in a
3015         pcre_callout  block  is  NULL. There is a description of the pcre_extra         pcre_callout block is NULL. There is a description  of  the  pcre_extra
3016         structure in the pcreapi documentation.         structure in the pcreapi documentation.
3017    
3018         The pattern_position field is present from version 1 of the  pcre_call-         The  pattern_position field is present from version 1 of the pcre_call-
3019         out structure. It contains the offset to the next item to be matched in         out structure. It contains the offset to the next item to be matched in
3020         the pattern string.         the pattern string.
3021    
3022         The next_item_length field is present from version 1 of the  pcre_call-         The  next_item_length field is present from version 1 of the pcre_call-
3023         out structure. It contains the length of the next item to be matched in         out structure. It contains the length of the next item to be matched in
3024         the pattern string. When the callout immediately precedes  an  alterna-         the  pattern  string. When the callout immediately precedes an alterna-
3025         tion  bar, a closing parenthesis, or the end of the pattern, the length         tion bar, a closing parenthesis, or the end of the pattern, the  length
3026         is zero. When the callout precedes an opening parenthesis,  the  length         is  zero.  When the callout precedes an opening parenthesis, the length
3027         is that of the entire subpattern.         is that of the entire subpattern.
3028    
3029         The  pattern_position  and next_item_length fields are intended to help         The pattern_position and next_item_length fields are intended  to  help
3030         in distinguishing between different automatic callouts, which all  have         in  distinguishing between different automatic callouts, which all have
3031         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
3032    
3033    
3034  RETURN VALUES  RETURN VALUES
3035    
3036         The  external callout function returns an integer to PCRE. If the value         The external callout function returns an integer to PCRE. If the  value
3037         is zero, matching proceeds as normal. If  the  value  is  greater  than         is  zero,  matching  proceeds  as  normal. If the value is greater than
3038         zero,  matching  fails  at  the current point, but the testing of other         zero, matching fails at the current point, but  the  testing  of  other
3039         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3040         failed.  If  the  value  is less than zero, the match is abandoned, and         failed. If the value is less than zero, the  match  is  abandoned,  and
3041         pcre_exec() or pcre_dfa_exec() returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3042    
3043         Negative  values  should  normally  be   chosen   from   the   set   of         Negative   values   should   normally   be   chosen  from  the  set  of
3044         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
3045         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
3046         reserved  for  use  by callout functions; it will never be used by PCRE         reserved for use by callout functions; it will never be  used  by  PCRE
3047         itself.         itself.
3048    
3049    
# Line 3043  AUTHOR Line 3056  AUTHOR
3056    
3057  REVISION  REVISION
3058    
3059         Last updated: 29 September 2009         Last updated: 21 November 2010
3060         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
3061  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3062    
3063    
3064  PCRECOMPAT(3)                                                    PCRECOMPAT(3)  PCRECOMPAT(3)                                                    PCRECOMPAT(3)
3065    
3066    
# Line 3202  REVISION Line 3215  REVISION
3215         Last updated: 31 October 2010         Last updated: 31 October 2010
3216         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
3217  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3218    
3219    
3220  PCREPATTERN(3)                                                  PCREPATTERN(3)  PCREPATTERN(3)                                                  PCREPATTERN(3)
3221    
3222    
# Line 3252  PCRE REGULAR EXPRESSION DETAILS Line 3265  PCRE REGULAR EXPRESSION DETAILS
3265         character types, instead of recognizing only characters with codes less         character types, instead of recognizing only characters with codes less
3266         than 128 via a lookup table.         than 128 via a lookup table.
3267    
3268         The remainder of this document discusses the  patterns  that  are  sup-         If a pattern starts with (*NO_START_OPT), it has  the  same  effect  as
3269         ported  by  PCRE when its main matching function, pcre_exec(), is used.         setting the PCRE_NO_START_OPTIMIZE option either at compile or matching
3270         From  release  6.0,   PCRE   offers   a   second   matching   function,         time. There are also some more of these special sequences that are con-
3271         pcre_dfa_exec(),  which matches using a different algorithm that is not         cerned with the handling of newlines; they are described below.
3272    
3273           The  remainder  of  this  document discusses the patterns that are sup-
3274           ported by PCRE when its main matching function, pcre_exec(),  is  used.
3275           From   release   6.0,   PCRE   offers   a   second  matching  function,
3276           pcre_dfa_exec(), which matches using a different algorithm that is  not
3277         Perl-compatible. Some of the features discussed below are not available         Perl-compatible. Some of the features discussed below are not available
3278         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the         when pcre_dfa_exec() is used. The advantages and disadvantages  of  the
3279         alternative function, and how it differs from the normal function,  are         alternative  function, and how it differs from the normal function, are
3280         discussed in the pcrematching page.         discussed in the pcrematching page.
3281    
3282    
3283  NEWLINE CONVENTIONS  NEWLINE CONVENTIONS
3284    
3285         PCRE  supports five different conventions for indicating line breaks in         PCRE supports five different conventions for indicating line breaks  in
3286         strings: a single CR (carriage return) character, a  single  LF  (line-         strings:  a  single  CR (carriage return) character, a single LF (line-
3287         feed) character, the two-character sequence CRLF, any of the three pre-         feed) character, the two-character sequence CRLF, any of the three pre-
3288         ceding, or any Unicode newline sequence. The pcreapi page  has  further         ceding,  or  any Unicode newline sequence. The pcreapi page has further
3289         discussion  about newlines, and shows how to set the newline convention         discussion about newlines, and shows how to set the newline  convention
3290         in the options arguments for the compiling and matching functions.         in the options arguments for the compiling and matching functions.
3291    
3292         It is also possible to specify a newline convention by starting a  pat-         It  is also possible to specify a newline convention by starting a pat-
3293         tern string with one of the following five sequences:         tern string with one of the following five sequences:
3294    
3295           (*CR)        carriage return           (*CR)        carriage return
# Line 3280  NEWLINE CONVENTIONS Line 3298  NEWLINE CONVENTIONS
3298           (*ANYCRLF)   any of the three above           (*ANYCRLF)   any of the three above
3299           (*ANY)       all Unicode newline sequences           (*ANY)       all Unicode newline sequences
3300    
3301         These  override  the default and the options given to pcre_compile() or         These override the default and the options given to  pcre_compile()  or
3302         pcre_compile2(). For example, on a Unix system where LF is the  default         pcre_compile2().  For example, on a Unix system where LF is the default
3303         newline sequence, the pattern         newline sequence, the pattern
3304    
3305           (*CR)a.b           (*CR)a.b
3306    
3307         changes the convention to CR. That pattern matches "a\nb" because LF is         changes the convention to CR. That pattern matches "a\nb" because LF is
3308         no longer a newline. Note that these special settings,  which  are  not         no  longer  a  newline. Note that these special settings, which are not
3309         Perl-compatible,  are  recognized  only at the very start of a pattern,         Perl-compatible, are recognized only at the very start  of  a  pattern,
3310         and that they must be in upper case.  If  more  than  one  of  them  is         and  that  they  must  be  in  upper  case. If more than one of them is
3311         present, the last one is used.         present, the last one is used.
3312    
3313         The  newline convention affects the interpretation of the dot metachar-         The newline convention affects the interpretation of the dot  metachar-
3314         acter when PCRE_DOTALL is not set, and also the behaviour of  \N.  How-         acter  when  PCRE_DOTALL is not set, and also the behaviour of \N. How-
3315         ever,  it  does  not  affect  what  the  \R escape sequence matches. By         ever, it does not affect  what  the  \R  escape  sequence  matches.  By
3316         default, this is any Unicode newline sequence, for Perl  compatibility.         default,  this is any Unicode newline sequence, for Perl compatibility.
3317         However,  this can be changed; see the description of \R in the section         However, this can be changed; see the description of \R in the  section
3318         entitled "Newline sequences" below. A change of \R setting can be  com-         entitled  "Newline sequences" below. A change of \R setting can be com-
3319         bined with a change of newline convention.         bined with a change of newline convention.
3320    
3321    
3322  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3323    
3324         A  regular  expression  is  a pattern that is matched against a subject         A regular expression is a pattern that is  matched  against  a  subject
3325         string from left to right. Most characters stand for  themselves  in  a         string  from  left  to right. Most characters stand for themselves in a
3326         pattern,  and  match  the corresponding characters in the subject. As a         pattern, and match the corresponding characters in the  subject.  As  a
3327         trivial example, the pattern         trivial example, the pattern
3328    
3329           The quick brown fox           The quick brown fox
3330    
3331         matches a portion of a subject string that is identical to itself. When         matches a portion of a subject string that is identical to itself. When
3332         caseless  matching is specified (the PCRE_CASELESS option), letters are         caseless matching is specified (the PCRE_CASELESS option), letters  are
3333         matched independently of case. In UTF-8 mode, PCRE  always  understands         matched  independently  of case. In UTF-8 mode, PCRE always understands
3334         the  concept  of case for characters whose values are less than 128, so         the concept of case for characters whose values are less than  128,  so
3335         caseless matching is always possible. For characters with  higher  val-         caseless  matching  is always possible. For characters with higher val-
3336         ues,  the concept of case is supported if PCRE is compiled with Unicode         ues, the concept of case is supported if PCRE is compiled with  Unicode
3337         property support, but not otherwise.   If  you  want  to  use  caseless         property  support,  but  not  otherwise.   If  you want to use caseless
3338         matching  for  characters  128  and above, you must ensure that PCRE is         matching for characters 128 and above, you must  ensure  that  PCRE  is
3339         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3340    
3341         The power of regular expressions comes  from  the  ability  to  include         The  power  of  regular  expressions  comes from the ability to include
3342         alternatives  and  repetitions in the pattern. These are encoded in the         alternatives and repetitions in the pattern. These are encoded  in  the
3343         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3344         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3345    
3346         There  are  two different sets of metacharacters: those that are recog-         There are two different sets of metacharacters: those that  are  recog-
3347         nized anywhere in the pattern except within square brackets, and  those         nized  anywhere in the pattern except within square brackets, and those
3348         that  are  recognized  within square brackets. Outside square brackets,         that are recognized within square brackets.  Outside  square  brackets,
3349         the metacharacters are as follows:         the metacharacters are as follows:
3350    
3351           \      general escape character with several uses           \      general escape character with several uses
# Line 3346  CHARACTERS AND METACHARACTERS Line 3364  CHARACTERS AND METACHARACTERS
3364                  also "possessive quantifier"                  also "possessive quantifier"
3365           {      start min/max quantifier           {      start min/max quantifier
3366    
3367         Part of a pattern that is in square brackets  is  called  a  "character         Part  of  a  pattern  that is in square brackets is called a "character
3368         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3369    
3370           \      general escape character           \      general escape character
# Line 3362  CHARACTERS AND METACHARACTERS Line 3380  CHARACTERS AND METACHARACTERS
3380  BACKSLASH  BACKSLASH
3381    
3382         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3383         a non-alphanumeric character, it takes away any  special  meaning  that         a character that is not a number or a letter, it takes away any special
3384         character  may  have.  This  use  of  backslash  as an escape character         meaning that character may have. This use of  backslash  as  an  escape
3385         applies both inside and outside character classes.         character applies both inside and outside character classes.
3386    
3387         For example, if you want to match a * character, you write  \*  in  the         For  example,  if  you want to match a * character, you write \* in the
3388         pattern.   This  escaping  action  applies whether or not the following         pattern.  This escaping action applies whether  or  not  the  following
3389         character would otherwise be interpreted as a metacharacter, so  it  is         character  would  otherwise be interpreted as a metacharacter, so it is
3390         always  safe  to  precede  a non-alphanumeric with backslash to specify         always safe to precede a non-alphanumeric  with  backslash  to  specify
3391         that it stands for itself. In particular, if you want to match a  back-         that  it stands for itself. In particular, if you want to match a back-
3392         slash, you write \\.         slash, you write \\.
3393    
3394         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in         In UTF-8 mode, only ASCII numbers and letters have any special  meaning
3395         the pattern (other than in a character class) and characters between  a         after  a  backslash.  All  other characters (in particular, those whose
3396           codepoints are greater than 127) are treated as literals.
3397    
3398           If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
3399           the  pattern (other than in a character class) and characters between a
3400         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
3401         ing backslash can be used to include a whitespace  or  #  character  as         ing  backslash  can  be  used to include a whitespace or # character as
3402         part of the pattern.         part of the pattern.
3403    
3404         If  you  want  to remove the special meaning from a sequence of charac-         If you want to remove the special meaning from a  sequence  of  charac-
3405         ters, you can do so by putting them between \Q and \E. This is  differ-         ters,  you can do so by putting them between \Q and \E. This is differ-
3406         ent  from  Perl  in  that  $  and  @ are handled as literals in \Q...\E         ent from Perl in that $ and  @  are  handled  as  literals  in  \Q...\E
3407         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-
3408         tion. Note the following examples:         tion. Note the following examples:
3409    
3410           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 3392  BACKSLASH Line 3414  BACKSLASH
3414           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3415           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3416    
3417         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
3418         classes.  An isolated \E that is not preceded by \Q is ignored.         classes.  An isolated \E that is not preceded by \Q is ignored.
3419    
3420     Non-printing characters     Non-printing characters
3421    
3422         A second use of backslash provides a way of encoding non-printing char-         A second use of backslash provides a way of encoding non-printing char-
3423         acters  in patterns in a visible manner. There is no restriction on the         acters in patterns in a visible manner. There is no restriction on  the
3424         appearance of non-printing characters, apart from the binary zero  that         appearance  of non-printing characters, apart from the binary zero that
3425         terminates  a  pattern,  but  when  a pattern is being prepared by text         terminates a pattern, but when a pattern  is  being  prepared  by  text
3426         editing, it is  often  easier  to  use  one  of  the  following  escape         editing,  it  is  often  easier  to  use  one  of  the following escape
3427         sequences than the binary character it represents:         sequences than the binary character it represents:
3428    
3429           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3430           \cx       "control-x", where x is any character           \cx       "control-x", where x is any ASCII character
3431           \e        escape (hex 1B)           \e        escape (hex 1B)
3432           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3433           \n        linefeed (hex 0A)           \n        linefeed (hex 0A)
# Line 3415  BACKSLASH Line 3437  BACKSLASH
3437           \xhh      character with hex code hh           \xhh      character with hex code hh
3438           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3439    
3440         The  precise  effect of \cx is as follows: if x is a lower case letter,         The precise effect of \cx is as follows: if x is a lower  case  letter,
3441         it is converted to upper case. Then bit 6 of the character (hex 40)  is         it  is converted to upper case. Then bit 6 of the character (hex 40) is
3442         inverted.   Thus  \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;         inverted.  Thus \cz becomes hex 1A (z is 7A), but \c{ becomes hex 3B ({
3443         becomes hex 7B.         is  7B),  while  \c; becomes hex 7B (; is 3B). If the byte following \c
3444           has a value greater than 127, a compile-time error occurs.  This  locks
3445         After \x, from zero to two hexadecimal digits are read (letters can  be         out  non-ASCII  characters in both byte mode and UTF-8 mode. (When PCRE
3446         in  upper  or  lower case). Any number of hexadecimal digits may appear         is compiled in EBCDIC mode, all byte values are  valid.  A  lower  case
3447         between \x{ and }, but the value of the character  code  must  be  less         letter is converted to upper case, and then the 0xc0 bits are flipped.)
3448    
3449           After  \x, from zero to two hexadecimal digits are read (letters can be
3450           in upper or lower case). Any number of hexadecimal  digits  may  appear
3451           between  \x{  and  },  but the value of the character code must be less
3452         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
3453         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
3454         than the largest Unicode code point, which is 10FFFF.         than the largest Unicode code point, which is 10FFFF.
3455    
3456         If  characters  other than hexadecimal digits appear between \x{ and },         If characters other than hexadecimal digits appear between \x{  and  },
3457         or if there is no terminating }, this form of escape is not recognized.         or if there is no terminating }, this form of escape is not recognized.
3458         Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal         Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal
3459         escape, with no following digits, giving a  character  whose  value  is         escape,  with  no  following  digits, giving a character whose value is
3460         zero.         zero.
3461    
3462         Characters whose value is less than 256 can be defined by either of the         Characters whose value is less than 256 can be defined by either of the
3463         two syntaxes for \x. There is no difference in the way  they  are  han-         two  syntaxes  for  \x. There is no difference in the way they are han-
3464         dled. For example, \xdc is exactly the same as \x{dc}.         dled. For example, \xdc is exactly the same as \x{dc}.
3465    
3466         After  \0  up  to two further octal digits are read. If there are fewer         After \0 up to two further octal digits are read. If  there  are  fewer
3467         than two digits, just  those  that  are  present  are  used.  Thus  the         than  two  digits,  just  those  that  are  present  are used. Thus the
3468         sequence \0\x\07 specifies two binary zeros followed by a BEL character         sequence \0\x\07 specifies two binary zeros followed by a BEL character
3469         (code value 7). Make sure you supply two digits after the initial  zero         (code  value 7). Make sure you supply two digits after the initial zero
3470         if the pattern character that follows is itself an octal digit.         if the pattern character that follows is itself an octal digit.
3471    
3472         The handling of a backslash followed by a digit other than 0 is compli-         The handling of a backslash followed by a digit other than 0 is compli-
3473         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3474         its  as  a  decimal  number. If the number is less than 10, or if there         its as a decimal number. If the number is less than  10,  or  if  there
3475         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3476         expression,  the  entire  sequence  is  taken  as  a  back reference. A         expression, the entire  sequence  is  taken  as  a  back  reference.  A
3477         description of how this works is given later, following the  discussion         description  of how this works is given later, following the discussion
3478         of parenthesized subpatterns.         of parenthesized subpatterns.
3479    
3480         Inside  a  character  class, or if the decimal number is greater than 9         Inside a character class, or if the decimal number is  greater  than  9
3481         and there have not been that many capturing subpatterns, PCRE  re-reads         and  there have not been that many capturing subpatterns, PCRE re-reads
3482         up to three octal digits following the backslash, and uses them to gen-         up to three octal digits following the backslash, and uses them to gen-
3483         erate a data character. Any subsequent digits stand for themselves.  In         erate  a data character. Any subsequent digits stand for themselves. In
3484         non-UTF-8  mode,  the  value  of a character specified in octal must be         non-UTF-8 mode, the value of a character specified  in  octal  must  be
3485         less than \400. In UTF-8 mode, values up to  \777  are  permitted.  For         less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For
3486         example:         example:
3487    
3488           \040   is another way of writing a space           \040   is another way of writing a space
# Line 3474  BACKSLASH Line 3500  BACKSLASH
3500           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3501                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3502    
3503         Note  that  octal  values of 100 or greater must not be introduced by a         Note that octal values of 100 or greater must not be  introduced  by  a
3504         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3505    
3506         All the sequences that define a single character value can be used both         All the sequences that define a single character value can be used both
3507         inside  and  outside character classes. In addition, inside a character         inside and outside character classes. In addition, inside  a  character
3508         class, the sequence \b is interpreted as the backspace  character  (hex         class,  the  sequence \b is interpreted as the backspace character (hex
3509         08).  The sequences \B, \N, \R, and \X are not special inside a charac-         08). The sequences \B, \N, \R, and \X are not special inside a  charac-
3510         ter class. Like any  other  unrecognized  escape  sequences,  they  are         ter  class.  Like  any  other  unrecognized  escape sequences, they are
3511         treated  as  the  literal characters "B", "N", "R", and "X" by default,         treated as the literal characters "B", "N", "R", and  "X"  by  default,
3512         but cause an error if the PCRE_EXTRA option is set. Outside a character         but cause an error if the PCRE_EXTRA option is set. Outside a character
3513         class, these sequences have different meanings.         class, these sequences have different meanings.
3514    
3515     Absolute and relative back references     Absolute and relative back references
3516    
3517         The  sequence  \g followed by an unsigned or a negative number, option-         The sequence \g followed by an unsigned or a negative  number,  option-
3518         ally enclosed in braces, is an absolute or relative back  reference.  A         ally  enclosed  in braces, is an absolute or relative back reference. A
3519         named back reference can be coded as \g{name}. Back references are dis-         named back reference can be coded as \g{name}. Back references are dis-
3520         cussed later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3521    
3522     Absolute and relative subroutine calls     Absolute and relative subroutine calls
3523    
3524         For compatibility with Oniguruma, the non-Perl syntax \g followed by  a         For  compatibility with Oniguruma, the non-Perl syntax \g followed by a
3525         name or a number enclosed either in angle brackets or single quotes, is         name or a number enclosed either in angle brackets or single quotes, is
3526         an alternative syntax for referencing a subpattern as  a  "subroutine".         an  alternative  syntax for referencing a subpattern as a "subroutine".
3527         Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and         Details are discussed later.   Note  that  \g{...}  (Perl  syntax)  and
3528         \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back         \g<...>  (Oniguruma  syntax)  are  not synonymous. The former is a back
3529         reference; the latter is a subroutine call.         reference; the latter is a subroutine call.
3530    
3531     Generic character types     Generic character types
# Line 3518  BACKSLASH Line 3544  BACKSLASH
3544           \W     any "non-word" character           \W     any "non-word" character
3545    
3546         There is also the single sequence \N, which matches a non-newline char-         There is also the single sequence \N, which matches a non-newline char-
3547         acter.  This is the same as the "." metacharacter when  PCRE_DOTALL  is         acter.   This  is the same as the "." metacharacter when PCRE_DOTALL is
3548         not set.         not set.
3549    
3550         Each  pair of lower and upper case escape sequences partitions the com-         Each pair of lower and upper case escape sequences partitions the  com-
3551         plete set of characters into two disjoint  sets.  Any  given  character         plete  set  of  characters  into two disjoint sets. Any given character
3552         matches  one, and only one, of each pair. The sequences can appear both         matches one, and only one, of each pair. The sequences can appear  both
3553         inside and outside character classes. They each match one character  of         inside  and outside character classes. They each match one character of
3554         the  appropriate  type.  If the current matching point is at the end of         the appropriate type. If the current matching point is at  the  end  of
3555         the subject string, all of them fail, because there is no character  to         the  subject string, all of them fail, because there is no character to
3556         match.         match.
3557    
3558         For  compatibility  with Perl, \s does not match the VT character (code         For compatibility with Perl, \s does not match the VT  character  (code
3559         11).  This makes it different from the the POSIX "space" class. The  \s         11).   This makes it different from the the POSIX "space" class. The \s
3560         characters  are  HT  (9), LF (10), FF (12), CR (13), and space (32). If         characters are HT (9), LF (10), FF (12), CR (13), and  space  (32).  If
3561         "use locale;" is included in a Perl script, \s may match the VT charac-         "use locale;" is included in a Perl script, \s may match the VT charac-
3562         ter. In PCRE, it never does.         ter. In PCRE, it never does.
3563    
3564         A  "word"  character is an underscore or any character that is a letter         A "word" character is an underscore or any character that is  a  letter
3565         or digit.  By default, the definition of letters  and  digits  is  con-         or  digit.   By  default,  the definition of letters and digits is con-
3566         trolled  by PCRE's low-valued character tables, and may vary if locale-         trolled by PCRE's low-valued character tables, and may vary if  locale-
3567         specific matching is taking place (see "Locale support" in the  pcreapi         specific  matching is taking place (see "Locale support" in the pcreapi
3568         page).  For  example,  in  a French locale such as "fr_FR" in Unix-like         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3569         systems, or "french" in Windows, some character codes greater than  128         systems,  or "french" in Windows, some character codes greater than 128
3570         are  used  for  accented letters, and these are then matched by \w. The         are used for accented letters, and these are then matched  by  \w.  The
3571         use of locales with Unicode is discouraged.         use of locales with Unicode is discouraged.
3572    
3573         By default, in UTF-8 mode, characters  with  values  greater  than  128         By  default,  in  UTF-8  mode,  characters with values greater than 128
3574         never  match  \d,  \s,  or  \w,  and always match \D, \S, and \W. These         never match \d, \s, or \w, and always  match  \D,  \S,  and  \W.  These
3575         sequences retain their original meanings from before UTF-8 support  was         sequences  retain their original meanings from before UTF-8 support was
3576         available,  mainly for efficiency reasons. However, if PCRE is compiled         available, mainly for efficiency reasons. However, if PCRE is  compiled
3577         with Unicode property support, and the PCRE_UCP option is set, the  be-         with  Unicode property support, and the PCRE_UCP option is set, the be-
3578         haviour  is  changed  so  that Unicode properties are used to determine         haviour is changed so that Unicode properties  are  used  to  determine
3579         character types, as follows:         character types, as follows:
3580    
3581           \d  any character that \p{Nd} matches (decimal digit)           \d  any character that \p{Nd} matches (decimal digit)
3582           \s  any character that \p{Z} matches, plus HT, LF, FF, CR           \s  any character that \p{Z} matches, plus HT, LF, FF, CR
3583           \w  any character that \p{L} or \p{N} matches, plus underscore           \w  any character that \p{L} or \p{N} matches, plus underscore
3584    
3585         The upper case escapes match the inverse sets of characters. Note  that         The  upper case escapes match the inverse sets of characters. Note that
3586         \d  matches  only decimal digits, whereas \w matches any Unicode digit,         \d matches only decimal digits, whereas \w matches any  Unicode  digit,
3587         as well as any Unicode letter, and underscore. Note also that  PCRE_UCP         as  well as any Unicode letter, and underscore. Note also that PCRE_UCP
3588         affects  \b,  and  \B  because  they are defined in terms of \w and \W.         affects \b, and \B because they are defined in  terms  of  \w  and  \W.
3589         Matching these sequences is noticeably slower when PCRE_UCP is set.         Matching these sequences is noticeably slower when PCRE_UCP is set.
3590    
3591         The sequences \h, \H, \v, and \V are features that were added  to  Perl         The  sequences  \h, \H, \v, and \V are features that were added to Perl
3592         at  release  5.10. In contrast to the other sequences, which match only         at release 5.10. In contrast to the other sequences, which  match  only
3593         ASCII characters by default, these  always  match  certain  high-valued         ASCII  characters  by  default,  these always match certain high-valued
3594         codepoints  in UTF-8 mode, whether or not PCRE_UCP is set. The horizon-         codepoints in UTF-8 mode, whether or not PCRE_UCP is set. The  horizon-
3595         tal space characters are:         tal space characters are:
3596    
3597           U+0009     Horizontal tab           U+0009     Horizontal tab
# Line 3600  BACKSLASH Line 3626  BACKSLASH
3626    
3627     Newline sequences     Newline sequences
3628    
3629         Outside a character class, by default, the escape sequence  \R  matches         Outside  a  character class, by default, the escape sequence \R matches
3630         any Unicode newline sequence. In non-UTF-8 mode \R is equivalent to the         any Unicode newline sequence. In non-UTF-8 mode \R is equivalent to the
3631         following:         following:
3632    
3633           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3634    
3635         This is an example of an "atomic group", details  of  which  are  given         This  is  an  example  of an "atomic group", details of which are given
3636         below.  This particular group matches either the two-character sequence         below.  This particular group matches either the two-character sequence
3637         CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,         CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,
3638         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
3639         return, U+000D), or NEL (next line, U+0085). The two-character sequence         return, U+000D), or NEL (next line, U+0085). The two-character sequence
3640         is treated as a single unit that cannot be split.         is treated as a single unit that cannot be split.
3641    
3642         In  UTF-8  mode, two additional characters whose codepoints are greater         In UTF-8 mode, two additional characters whose codepoints  are  greater
3643         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
3644         rator,  U+2029).   Unicode character property support is not needed for         rator, U+2029).  Unicode character property support is not  needed  for
3645         these characters to be recognized.         these characters to be recognized.
3646    
3647         It is possible to restrict \R to match only CR, LF, or CRLF (instead of         It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3648         the  complete  set  of  Unicode  line  endings)  by  setting the option         the complete set  of  Unicode  line  endings)  by  setting  the  option
3649         PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.         PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3650         (BSR is an abbrevation for "backslash R".) This can be made the default         (BSR is an abbrevation for "backslash R".) This can be made the default
3651         when PCRE is built; if this is the case, the  other  behaviour  can  be         when  PCRE  is  built;  if this is the case, the other behaviour can be
3652         requested  via  the  PCRE_BSR_UNICODE  option.   It is also possible to         requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
3653         specify these settings by starting a pattern string  with  one  of  the         specify  these  settings  by  starting a pattern string with one of the
3654         following sequences:         following sequences:
3655    
3656           (*BSR_ANYCRLF)   CR, LF, or CRLF only           (*BSR_ANYCRLF)   CR, LF, or CRLF only
3657           (*BSR_UNICODE)   any Unicode newline sequence           (*BSR_UNICODE)   any Unicode newline sequence
3658    
3659         These  override  the default and the options given to pcre_compile() or         These override the default and the options given to  pcre_compile()  or
3660         pcre_compile2(), but  they  can  be  overridden  by  options  given  to         pcre_compile2(),  but  they  can  be  overridden  by  options  given to
3661         pcre_exec() or pcre_dfa_exec(). Note that these special settings, which         pcre_exec() or pcre_dfa_exec(). Note that these special settings, which
3662         are not Perl-compatible, are recognized only at the  very  start  of  a         are  not  Perl-compatible,  are  recognized only at the very start of a
3663         pattern,  and that they must be in upper case. If more than one of them         pattern, and that they must be in upper case. If more than one of  them
3664         is present, the last one is used. They can be combined with a change of         is present, the last one is used. They can be combined with a change of
3665         newline convention; for example, a pattern can start with:         newline convention; for example, a pattern can start with:
3666    
3667           (*ANY)(*BSR_ANYCRLF)           (*ANY)(*BSR_ANYCRLF)
3668    
3669         They can also be combined with the (*UTF8) or (*UCP) special sequences.         They can also be combined with the (*UTF8) or (*UCP) special sequences.
3670         Inside a character class, \R  is  treated  as  an  unrecognized  escape         Inside  a  character  class,  \R  is  treated as an unrecognized escape
3671         sequence, and so matches the letter "R" by default, but causes an error         sequence, and so matches the letter "R" by default, but causes an error
3672         if PCRE_EXTRA is set.         if PCRE_EXTRA is set.
3673    
3674     Unicode character properties     Unicode character properties
3675    
3676         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3677         tional  escape sequences that match characters with specific properties         tional escape sequences that match characters with specific  properties
3678         are available.  When not in UTF-8 mode, these sequences are  of  course         are  available.   When not in UTF-8 mode, these sequences are of course
3679         limited  to  testing characters whose codepoints are less than 256, but         limited to testing characters whose codepoints are less than  256,  but
3680         they do work in this mode.  The extra escape sequences are:         they do work in this mode.  The extra escape sequences are:
3681    
3682           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3683           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
3684           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3685    
3686         The property names represented by xx above are limited to  the  Unicode         The  property  names represented by xx above are limited to the Unicode
3687         script names, the general category properties, "Any", which matches any         script names, the general category properties, "Any", which matches any
3688         character  (including  newline),  and  some  special  PCRE   properties         character   (including  newline),  and  some  special  PCRE  properties
3689         (described  in the next section).  Other Perl properties such as "InMu-         (described in the next section).  Other Perl properties such as  "InMu-
3690         sicalSymbols" are not currently supported by PCRE.  Note  that  \P{Any}         sicalSymbols"  are  not  currently supported by PCRE. Note that \P{Any}
3691         does not match any characters, so always causes a match failure.         does not match any characters, so always causes a match failure.
3692    
3693         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3694         A character from one of these sets can be matched using a script  name.         A  character from one of these sets can be matched using a script name.
3695         For example:         For example:
3696    
3697           \p{Greek}           \p{Greek}
3698           \P{Han}           \P{Han}
3699    
3700         Those  that are not part of an identified script are lumped together as         Those that are not part of an identified script are lumped together  as
3701         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3702    
3703         Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,         Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,
3704         Buginese,  Buhid,  Canadian_Aboriginal, Carian, Cham, Cherokee, Common,         Buginese, Buhid, Canadian_Aboriginal, Carian, Cham,  Cherokee,  Common,
3705         Coptic,  Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,   Egyp-         Coptic,   Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,  Egyp-
3706         tian_Hieroglyphs,   Ethiopic,   Georgian,  Glagolitic,  Gothic,  Greek,         tian_Hieroglyphs,  Ethiopic,  Georgian,  Glagolitic,   Gothic,   Greek,
3707         Gujarati, Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana,  Impe-         Gujarati,  Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana, Impe-
3708         rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,         rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,
3709         Javanese, Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer,  Lao,         Javanese,  Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao,
3710         Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,         Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,
3711         Meetei_Mayek, Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham,  Old_Italic,         Meetei_Mayek,  Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic,
3712         Old_Persian,  Old_South_Arabian,  Old_Turkic, Ol_Chiki, Oriya, Osmanya,         Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki,  Oriya,  Osmanya,
3713         Phags_Pa, Phoenician, Rejang, Runic,  Samaritan,  Saurashtra,  Shavian,         Phags_Pa,  Phoenician,  Rejang,  Runic, Samaritan, Saurashtra, Shavian,
3714         Sinhala,  Sundanese,  Syloti_Nagri,  Syriac, Tagalog, Tagbanwa, Tai_Le,         Sinhala, Sundanese, Syloti_Nagri, Syriac,  Tagalog,  Tagbanwa,  Tai_Le,
3715         Tai_Tham, Tai_Viet, Tamil, Telugu,  Thaana,  Thai,  Tibetan,  Tifinagh,         Tai_Tham,  Tai_Viet,  Tamil,  Telugu,  Thaana, Thai, Tibetan, Tifinagh,
3716         Ugaritic, Vai, Yi.         Ugaritic, Vai, Yi.
3717    
3718         Each character has exactly one Unicode general category property, spec-         Each character has exactly one Unicode general category property, spec-
3719         ified by a two-letter abbreviation. For compatibility with Perl,  nega-         ified  by a two-letter abbreviation. For compatibility with Perl, nega-
3720         tion  can  be  specified  by including a circumflex between the opening         tion can be specified by including a  circumflex  between  the  opening
3721         brace and the property name.  For  example,  \p{^Lu}  is  the  same  as         brace  and  the  property  name.  For  example,  \p{^Lu} is the same as
3722         \P{Lu}.         \P{Lu}.
3723    
3724         If only one letter is specified with \p or \P, it includes all the gen-         If only one letter is specified with \p or \P, it includes all the gen-
3725         eral category properties that start with that letter. In this case,  in         eral  category properties that start with that letter. In this case, in
3726         the  absence of negation, the curly brackets in the escape sequence are         the absence of negation, the curly brackets in the escape sequence  are
3727         optional; these two examples have the same effect:         optional; these two examples have the same effect:
3728    
3729           \p{L}           \p{L}
# Line 3749  BACKSLASH Line 3775  BACKSLASH
3775           Zp    Paragraph separator           Zp    Paragraph separator
3776           Zs    Space separator           Zs    Space separator
3777    
3778         The special property L& is also supported: it matches a character  that         The  special property L& is also supported: it matches a character that
3779         has  the  Lu,  Ll, or Lt property, in other words, a letter that is not         has the Lu, Ll, or Lt property, in other words, a letter  that  is  not
3780         classified as a modifier or "other".         classified as a modifier or "other".
3781    
3782         The Cs (Surrogate) property applies only to  characters  in  the  range         The  Cs  (Surrogate)  property  applies only to characters in the range
3783         U+D800  to  U+DFFF. Such characters are not valid in UTF-8 strings (see         U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
3784         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3785         ing  has  been  turned off (see the discussion of PCRE_NO_UTF8_CHECK in         ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
3786         the pcreapi page). Perl does not support the Cs property.         the pcreapi page). Perl does not support the Cs property.
3787    
3788         The long synonyms for  property  names  that  Perl  supports  (such  as         The  long  synonyms  for  property  names  that  Perl supports (such as
3789         \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix         \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix
3790         any of these properties with "Is".         any of these properties with "Is".
3791    
3792         No character that is in the Unicode table has the Cn (unassigned) prop-         No character that is in the Unicode table has the Cn (unassigned) prop-
3793         erty.  Instead, this property is assumed for any code point that is not         erty.  Instead, this property is assumed for any code point that is not
3794         in the Unicode table.         in the Unicode table.
3795    
3796         Specifying caseless matching does not affect  these  escape  sequences.         Specifying  caseless  matching  does not affect these escape sequences.
3797         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
3798    
3799         The  \X  escape  matches  any number of Unicode characters that form an         The \X escape matches any number of Unicode  characters  that  form  an
3800         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
3801    
3802           (?>\PM\pM*)           (?>\PM\pM*)
3803    
3804         That is, it matches a character without the "mark"  property,  followed         That  is,  it matches a character without the "mark" property, followed
3805         by  zero  or  more  characters with the "mark" property, and treats the         by zero or more characters with the "mark"  property,  and  treats  the
3806         sequence as an atomic group (see below).  Characters  with  the  "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
3807         property  are  typically  accents  that affect the preceding character.         property are typically accents that  affect  the  preceding  character.
3808         None of them have codepoints less than 256, so  in  non-UTF-8  mode  \X         None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
3809         matches any one character.         matches any one character.
3810    
3811         Matching  characters  by Unicode property is not fast, because PCRE has         Matching characters by Unicode property is not fast, because  PCRE  has
3812         to search a structure that contains  data  for  over  fifteen  thousand         to  search  a  structure  that  contains data for over fifteen thousand
3813         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3814         \w do not use Unicode properties in PCRE by  default,  though  you  can         \w  do  not  use  Unicode properties in PCRE by default, though you can
3815         make them do so by setting the PCRE_UCP option for pcre_compile() or by         make them do so by setting the PCRE_UCP option for pcre_compile() or by
3816         starting the pattern with (*UCP).         starting the pattern with (*UCP).
3817    
3818     PCRE's additional properties     PCRE's additional properties
3819    
3820         As well as the standard Unicode properties described  in  the  previous         As  well  as  the standard Unicode properties described in the previous
3821         section,  PCRE supports four more that make it possible to convert tra-         section, PCRE supports four more that make it possible to convert  tra-
3822         ditional escape sequences such as \w and \s and POSIX character classes         ditional escape sequences such as \w and \s and POSIX character classes
3823         to use Unicode properties. PCRE uses these non-standard, non-Perl prop-         to use Unicode properties. PCRE uses these non-standard, non-Perl prop-
3824         erties internally when PCRE_UCP is set. They are:         erties internally when PCRE_UCP is set. They are:
# Line 3802  BACKSLASH Line 3828  BACKSLASH
3828           Xsp   Any Perl space character           Xsp   Any Perl space character
3829           Xwd   Any Perl "word" character           Xwd   Any Perl "word" character
3830    
3831         Xan matches characters that have either the L (letter) or the  N  (num-         Xan  matches  characters that have either the L (letter) or the N (num-
3832         ber)  property. Xps matches the characters tab, linefeed, vertical tab,         ber) property. Xps matches the characters tab, linefeed, vertical  tab,
3833         formfeed, or carriage return, and any other character that  has  the  Z         formfeed,  or  carriage  return, and any other character that has the Z
3834         (separator) property.  Xsp is the same as Xps, except that vertical tab         (separator) property.  Xsp is the same as Xps, except that vertical tab
3835         is excluded. Xwd matches the same characters as Xan, plus underscore.         is excluded. Xwd matches the same characters as Xan, plus underscore.
3836    
3837     Resetting the match start     Resetting the match start
3838    
3839         The escape sequence \K causes any previously matched characters not  to         The  escape sequence \K causes any previously matched characters not to
3840         be included in the final matched sequence. For example, the pattern:         be included in the final matched sequence. For example, the pattern:
3841    
3842           foo\Kbar           foo\Kbar
3843    
3844         matches  "foobar",  but reports that it has matched "bar". This feature         matches "foobar", but reports that it has matched "bar".  This  feature
3845         is similar to a lookbehind assertion (described  below).   However,  in         is  similar  to  a lookbehind assertion (described below).  However, in
3846         this  case, the part of the subject before the real match does not have         this case, the part of the subject before the real match does not  have
3847         to be of fixed length, as lookbehind assertions do. The use of \K  does         to  be of fixed length, as lookbehind assertions do. The use of \K does
3848         not  interfere  with  the setting of captured substrings.  For example,         not interfere with the setting of captured  substrings.   For  example,
3849         when the pattern         when the pattern
3850    
3851           (foo)\Kbar           (foo)\Kbar
3852    
3853         matches "foobar", the first substring is still set to "foo".         matches "foobar", the first substring is still set to "foo".
3854    
3855         Perl documents that the use  of  \K  within  assertions  is  "not  well         Perl  documents  that  the  use  of  \K  within assertions is "not well
3856         defined".  In  PCRE,  \K  is  acted upon when it occurs inside positive         defined". In PCRE, \K is acted upon  when  it  occurs  inside  positive
3857         assertions, but is ignored in negative assertions.         assertions, but is ignored in negative assertions.
3858    
3859     Simple assertions     Simple assertions
3860    
3861         The final use of backslash is for certain simple assertions. An  asser-         The  final use of backslash is for certain simple assertions. An asser-
3862         tion  specifies a condition that has to be met at a particular point in         tion specifies a condition that has to be met at a particular point  in
3863         a match, without consuming any characters from the subject string.  The         a  match, without consuming any characters from the subject string. The
3864         use  of subpatterns for more complicated assertions is described below.         use of subpatterns for more complicated assertions is described  below.
3865         The backslashed assertions are:         The backslashed assertions are:
3866    
3867           \b     matches at a word boundary           \b     matches at a word boundary
# Line 3846  BACKSLASH Line 3872  BACKSLASH
3872           \z     matches only at the end of the subject           \z     matches only at the end of the subject
3873           \G     matches at the first matching position in the subject           \G     matches at the first matching position in the subject
3874    
3875         Inside a character class, \b has a different meaning;  it  matches  the         Inside  a  character  class, \b has a different meaning; it matches the
3876         backspace  character.  If  any  other  of these assertions appears in a         backspace character. If any other of  these  assertions  appears  in  a
3877         character class, by default it matches the corresponding literal  char-         character  class, by default it matches the corresponding literal char-
3878         acter  (for  example,  \B  matches  the  letter  B).  However,  if  the         acter  (for  example,  \B  matches  the  letter  B).  However,  if  the
3879         PCRE_EXTRA option is set, an "invalid escape sequence" error is  gener-         PCRE_EXTRA  option is set, an "invalid escape sequence" error is gener-
3880         ated instead.         ated instead.
3881    
3882         A  word  boundary is a position in the subject string where the current         A word boundary is a position in the subject string where  the  current
3883         character and the previous character do not both match \w or  \W  (i.e.         character  and  the previous character do not both match \w or \W (i.e.
3884         one  matches  \w  and the other matches \W), or the start or end of the         one matches \w and the other matches \W), or the start or  end  of  the
3885         string if the first or last  character  matches  \w,  respectively.  In         string  if  the  first  or  last character matches \w, respectively. In
3886         UTF-8  mode,  the  meanings  of \w and \W can be changed by setting the         UTF-8 mode, the meanings of \w and \W can be  changed  by  setting  the
3887         PCRE_UCP option. When this is done, it also affects \b and \B.  Neither         PCRE_UCP  option. When this is done, it also affects \b and \B. Neither
3888         PCRE  nor  Perl has a separate "start of word" or "end of word" metase-         PCRE nor Perl has a separate "start of word" or "end of  word"  metase-
3889         quence. However, whatever follows \b normally determines which  it  is.         quence.  However,  whatever follows \b normally determines which it is.
3890         For example, the fragment \ba matches "a" at the start of a word.         For example, the fragment \ba matches "a" at the start of a word.
3891    
3892         The  \A,  \Z,  and \z assertions differ from the traditional circumflex         The \A, \Z, and \z assertions differ from  the  traditional  circumflex
3893         and dollar (described in the next section) in that they only ever match         and dollar (described in the next section) in that they only ever match
3894         at  the  very start and end of the subject string, whatever options are         at the very start and end of the subject string, whatever  options  are
3895         set. Thus, they are independent of multiline mode. These  three  asser-         set.  Thus,  they are independent of multiline mode. These three asser-
3896         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which
3897         affect only the behaviour of the circumflex and dollar  metacharacters.         affect  only the behaviour of the circumflex and dollar metacharacters.
3898         However,  if the startoffset argument of pcre_exec() is non-zero, indi-         However, if the startoffset argument of pcre_exec() is non-zero,  indi-
3899         cating that matching is to start at a point other than the beginning of         cating that matching is to start at a point other than the beginning of
3900         the  subject,  \A  can never match. The difference between \Z and \z is         the subject, \A can never match. The difference between \Z  and  \z  is
3901         that \Z matches before a newline at the end of the string as well as at         that \Z matches before a newline at the end of the string as well as at
3902         the very end, whereas \z matches only at the end.         the very end, whereas \z matches only at the end.
3903    
3904         The  \G assertion is true only when the current matching position is at         The \G assertion is true only when the current matching position is  at
3905         the start point of the match, as specified by the startoffset  argument         the  start point of the match, as specified by the startoffset argument
3906         of  pcre_exec().  It  differs  from \A when the value of startoffset is         of pcre_exec(). It differs from \A when the  value  of  startoffset  is
3907         non-zero. By calling pcre_exec() multiple times with appropriate  argu-         non-zero.  By calling pcre_exec() multiple times with appropriate argu-
3908         ments, you can mimic Perl's /g option, and it is in this kind of imple-         ments, you can mimic Perl's /g option, and it is in this kind of imple-
3909         mentation where \G can be useful.         mentation where \G can be useful.
3910    
3911         Note, however, that PCRE's interpretation of \G, as the  start  of  the         Note,  however,  that  PCRE's interpretation of \G, as the start of the
3912         current match, is subtly different from Perl's, which defines it as the         current match, is subtly different from Perl's, which defines it as the
3913         end of the previous match. In Perl, these can  be  different  when  the         end  of  the  previous  match. In Perl, these can be different when the
3914         previously  matched  string was empty. Because PCRE does just one match         previously matched string was empty. Because PCRE does just  one  match
3915         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
3916    
3917         If all the alternatives of a pattern begin with \G, the  expression  is         If  all  the alternatives of a pattern begin with \G, the expression is
3918         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
3919         in the compiled regular expression.         in the compiled regular expression.
3920    
# Line 3896  BACKSLASH Line 3922  BACKSLASH
3922  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
3923    
3924         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
3925         character  is  an  assertion  that is true only if the current matching         character is an assertion that is true only  if  the  current  matching
3926         point is at the start of the subject string. If the  startoffset  argu-         point  is  at the start of the subject string. If the startoffset argu-
3927         ment  of  pcre_exec()  is  non-zero,  circumflex can never match if the         ment of pcre_exec() is non-zero, circumflex  can  never  match  if  the
3928         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex
3929         has an entirely different meaning (see below).         has an entirely different meaning (see below).
3930    
3931         Circumflex  need  not be the first character of the pattern if a number         Circumflex need not be the first character of the pattern if  a  number
3932         of alternatives are involved, but it should be the first thing in  each         of  alternatives are involved, but it should be the first thing in each
3933         alternative  in  which  it appears if the pattern is ever to match that         alternative in which it appears if the pattern is ever  to  match  that
3934         branch. If all possible alternatives start with a circumflex, that  is,         branch.  If all possible alternatives start with a circumflex, that is,
3935         if  the  pattern  is constrained to match only at the start of the sub-         if the pattern is constrained to match only at the start  of  the  sub-
3936         ject, it is said to be an "anchored" pattern.  (There  are  also  other         ject,  it  is  said  to be an "anchored" pattern. (There are also other
3937         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
3938    
3939         A  dollar  character  is  an assertion that is true only if the current         A dollar character is an assertion that is true  only  if  the  current
3940         matching point is at the end of  the  subject  string,  or  immediately         matching  point  is  at  the  end of the subject string, or immediately
3941         before a newline at the end of the string (by default). Dollar need not         before a newline at the end of the string (by default). Dollar need not
3942         be the last character of the pattern if a number  of  alternatives  are         be  the  last  character of the pattern if a number of alternatives are
3943         involved,  but  it  should  be  the last item in any branch in which it         involved, but it should be the last item in  any  branch  in  which  it
3944         appears. Dollar has no special meaning in a character class.         appears. Dollar has no special meaning in a character class.
3945    
3946         The meaning of dollar can be changed so that it  matches  only  at  the         The  meaning  of  dollar  can be changed so that it matches only at the
3947         very  end  of  the string, by setting the PCRE_DOLLAR_ENDONLY option at         very end of the string, by setting the  PCRE_DOLLAR_ENDONLY  option  at
3948         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
3949    
3950         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
3951         PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex         PCRE_MULTILINE option is set. When  this  is  the  case,  a  circumflex
3952         matches immediately after internal newlines as well as at the start  of         matches  immediately after internal newlines as well as at the start of
3953         the  subject  string.  It  does not match after a newline that ends the         the subject string. It does not match after a  newline  that  ends  the
3954         string. A dollar matches before any newlines in the string, as well  as         string.  A dollar matches before any newlines in the string, as well as
3955         at  the very end, when PCRE_MULTILINE is set. When newline is specified         at the very end, when PCRE_MULTILINE is set. When newline is  specified
3956         as the two-character sequence CRLF, isolated CR and  LF  characters  do         as  the  two-character  sequence CRLF, isolated CR and LF characters do
3957         not indicate newlines.         not indicate newlines.
3958    
3959         For  example, the pattern /^abc$/ matches the subject string "def\nabc"         For example, the pattern /^abc$/ matches the subject string  "def\nabc"
3960         (where \n represents a newline) in multiline mode, but  not  otherwise.         (where  \n  represents a newline) in multiline mode, but not otherwise.
3961         Consequently,  patterns  that  are anchored in single line mode because         Consequently, patterns that are anchored in single  line  mode  because
3962         all branches start with ^ are not anchored in  multiline  mode,  and  a         all  branches  start  with  ^ are not anchored in multiline mode, and a
3963         match  for  circumflex  is  possible  when  the startoffset argument of         match for circumflex is  possible  when  the  startoffset  argument  of
3964         pcre_exec() is non-zero. The PCRE_DOLLAR_ENDONLY option is  ignored  if         pcre_exec()  is  non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if
3965         PCRE_MULTILINE is set.         PCRE_MULTILINE is set.
3966    
3967         Note  that  the sequences \A, \Z, and \z can be used to match the start         Note that the sequences \A, \Z, and \z can be used to match  the  start
3968         and end of the subject in both modes, and if all branches of a  pattern         and  end of the subject in both modes, and if all branches of a pattern
3969         start  with  \A it is always anchored, whether or not PCRE_MULTILINE is         start with \A it is always anchored, whether or not  PCRE_MULTILINE  is
3970         set.         set.
3971    
3972    
3973  FULL STOP (PERIOD, DOT) AND \N  FULL STOP (PERIOD, DOT) AND \N
3974    
3975         Outside a character class, a dot in the pattern matches any one charac-         Outside a character class, a dot in the pattern matches any one charac-
3976         ter  in  the subject string except (by default) a character that signi-         ter in the subject string except (by default) a character  that  signi-
3977         fies the end of a line. In UTF-8 mode, the  matched  character  may  be         fies  the  end  of  a line. In UTF-8 mode, the matched character may be
3978         more than one byte long.         more than one byte long.
3979    
3980         When  a line ending is defined as a single character, dot never matches         When a line ending is defined as a single character, dot never  matches
3981         that character; when the two-character sequence CRLF is used, dot  does         that  character; when the two-character sequence CRLF is used, dot does
3982         not  match  CR  if  it  is immediately followed by LF, but otherwise it         not match CR if it is immediately followed  by  LF,  but  otherwise  it
3983         matches all characters (including isolated CRs and LFs). When any  Uni-         matches  all characters (including isolated CRs and LFs). When any Uni-
3984         code  line endings are being recognized, dot does not match CR or LF or         code line endings are being recognized, dot does not match CR or LF  or
3985         any of the other line ending characters.         any of the other line ending characters.
3986    
3987         The behaviour of dot with regard to newlines can  be  changed.  If  the         The  behaviour  of  dot  with regard to newlines can be changed. If the
3988         PCRE_DOTALL  option  is  set,  a dot matches any one character, without         PCRE_DOTALL option is set, a dot matches  any  one  character,  without
3989         exception. If the two-character sequence CRLF is present in the subject         exception. If the two-character sequence CRLF is present in the subject
3990         string, it takes two dots to match it.         string, it takes two dots to match it.
3991    
3992         The  handling of dot is entirely independent of the handling of circum-         The handling of dot is entirely independent of the handling of  circum-
3993         flex and dollar, the only relationship being  that  they  both  involve         flex  and  dollar,  the  only relationship being that they both involve
3994         newlines. Dot has no special meaning in a character class.         newlines. Dot has no special meaning in a character class.
3995    
3996         The  escape  sequence  \N  behaves  like  a  dot, except that it is not         The escape sequence \N behaves like  a  dot,  except  that  it  is  not
3997         affected by the PCRE_DOTALL option. In  other  words,  it  matches  any         affected  by  the  PCRE_DOTALL  option.  In other words, it matches any
3998         character except one that signifies the end of a line.         character except one that signifies the end of a line.
3999    
4000    
4001  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
4002    
4003         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
4004         both in and out of UTF-8 mode. Unlike a  dot,  it  always  matches  any         both  in  and  out  of  UTF-8 mode. Unlike a dot, it always matches any
4005         line-ending  characters.  The  feature  is provided in Perl in order to         line-ending characters. The feature is provided in  Perl  in  order  to
4006         match individual bytes in UTF-8 mode. Because it breaks up UTF-8  char-         match  individual bytes in UTF-8 mode. Because it breaks up UTF-8 char-
4007         acters  into  individual bytes, the rest of the string may start with a         acters into individual bytes, the rest of the string may start  with  a
4008         malformed UTF-8 character. For this reason, the \C escape  sequence  is         malformed  UTF-8  character. For this reason, the \C escape sequence is
4009         best avoided.         best avoided.
4010    
4011         PCRE  does  not  allow \C to appear in lookbehind assertions (described         PCRE does not allow \C to appear in  lookbehind  assertions  (described
4012         below), because in UTF-8 mode this would make it impossible  to  calcu-         below),  because  in UTF-8 mode this would make it impossible to calcu-
4013         late the length of the lookbehind.         late the length of the lookbehind.
4014    
4015    
# Line 3993  SQUARE BRACKETS AND CHARACTER CLASSES Line 4019  SQUARE BRACKETS AND CHARACTER CLASSES
4019         closing square bracket. A closing square bracket on its own is not spe-         closing square bracket. A closing square bracket on its own is not spe-
4020         cial by default.  However, if the PCRE_JAVASCRIPT_COMPAT option is set,         cial by default.  However, if the PCRE_JAVASCRIPT_COMPAT option is set,
4021         a lone closing square bracket causes a compile-time error. If a closing         a lone closing square bracket causes a compile-time error. If a closing
4022         square  bracket  is required as a member of the class, it should be the         square bracket is required as a member of the class, it should  be  the
4023         first data character in the class  (after  an  initial  circumflex,  if         first  data  character  in  the  class (after an initial circumflex, if
4024         present) or escaped with a backslash.         present) or escaped with a backslash.
4025    
4026         A  character  class matches a single character in the subject. In UTF-8         A character class matches a single character in the subject.  In  UTF-8
4027         mode, the character may be more than one byte long. A matched character         mode, the character may be more than one byte long. A matched character
4028         must be in the set of characters defined by the class, unless the first         must be in the set of characters defined by the class, unless the first
4029         character in the class definition is a circumflex, in  which  case  the         character  in  the  class definition is a circumflex, in which case the
4030         subject  character  must  not  be in the set defined by the class. If a         subject character must not be in the set defined by  the  class.  If  a
4031         circumflex is actually required as a member of the class, ensure it  is         circumflex  is actually required as a member of the class, ensure it is
4032         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
4033    
4034         For  example, the character class [aeiou] matches any lower case vowel,         For example, the character class [aeiou] matches any lower case  vowel,
4035         while [^aeiou] matches any character that is not a  lower  case  vowel.         while  [^aeiou]  matches  any character that is not a lower case vowel.
4036         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
4037         characters that are in the class by enumerating those that are  not.  A         characters  that  are in the class by enumerating those that are not. A
4038         class  that starts with a circumflex is not an assertion; it still con-         class that starts with a circumflex is not an assertion; it still  con-
4039         sumes a character from the subject string, and therefore  it  fails  if         sumes  a  character  from the subject string, and therefore it fails if
4040         the current pointer is at the end of the string.         the current pointer is at the end of the string.
4041    
4042         In  UTF-8 mode, characters with values greater than 255 can be included         In UTF-8 mode, characters with values greater than 255 can be  included
4043         in a class as a literal string of bytes, or by using the  \x{  escaping         in  a  class as a literal string of bytes, or by using the \x{ escaping
4044         mechanism.         mechanism.
4045    
4046         When  caseless  matching  is set, any letters in a class represent both         When caseless matching is set, any letters in a  class  represent  both
4047         their upper case and lower case versions, so for  example,  a  caseless         their  upper  case  and lower case versions, so for example, a caseless
4048         [aeiou]  matches  "A"  as well as "a", and a caseless [^aeiou] does not         [aeiou] matches "A" as well as "a", and a caseless  [^aeiou]  does  not
4049         match "A", whereas a caseful version would. In UTF-8 mode, PCRE  always         match  "A", whereas a caseful version would. In UTF-8 mode, PCRE always
4050         understands  the  concept  of case for characters whose values are less         understands the concept of case for characters whose  values  are  less
4051         than 128, so caseless matching is always possible. For characters  with         than  128, so caseless matching is always possible. For characters with
4052         higher  values,  the  concept  of case is supported if PCRE is compiled         higher values, the concept of case is supported  if  PCRE  is  compiled
4053         with Unicode property support, but not otherwise.  If you want  to  use         with  Unicode  property support, but not otherwise.  If you want to use
4054         caseless  matching  in UTF8-mode for characters 128 and above, you must         caseless matching in UTF8-mode for characters 128 and above,  you  must
4055         ensure that PCRE is compiled with Unicode property support as  well  as         ensure  that  PCRE is compiled with Unicode property support as well as
4056         with UTF-8 support.         with UTF-8 support.
4057    
4058         Characters  that  might  indicate  line breaks are never treated in any         Characters that might indicate line breaks are  never  treated  in  any
4059         special way  when  matching  character  classes,  whatever  line-ending         special  way  when  matching  character  classes,  whatever line-ending
4060         sequence  is  in  use,  and  whatever  setting  of  the PCRE_DOTALL and         sequence is in  use,  and  whatever  setting  of  the  PCRE_DOTALL  and
4061         PCRE_MULTILINE options is used. A class such as [^a] always matches one         PCRE_MULTILINE options is used. A class such as [^a] always matches one
4062         of these characters.         of these characters.
4063    
4064         The  minus (hyphen) character can be used to specify a range of charac-         The minus (hyphen) character can be used to specify a range of  charac-
4065         ters in a character  class.  For  example,  [d-m]  matches  any  letter         ters  in  a  character  class.  For  example,  [d-m] matches any letter
4066         between  d  and  m,  inclusive.  If  a minus character is required in a         between d and m, inclusive. If a  minus  character  is  required  in  a
4067         class, it must be escaped with a backslash  or  appear  in  a  position         class,  it  must  be  escaped  with a backslash or appear in a position
4068         where  it cannot be interpreted as indicating a range, typically as the         where it cannot be interpreted as indicating a range, typically as  the
4069         first or last character in the class.         first or last character in the class.
4070    
4071         It is not possible to have the literal character "]" as the end charac-         It is not possible to have the literal character "]" as the end charac-
4072         ter  of a range. A pattern such as [W-]46] is interpreted as a class of         ter of a range. A pattern such as [W-]46] is interpreted as a class  of
4073         two characters ("W" and "-") followed by a literal string "46]", so  it         two  characters ("W" and "-") followed by a literal string "46]", so it
4074         would  match  "W46]"  or  "-46]". However, if the "]" is escaped with a         would match "W46]" or "-46]". However, if the "]"  is  escaped  with  a
4075         backslash it is interpreted as the end of range, so [W-\]46] is  inter-         backslash  it is interpreted as the end of range, so [W-\]46] is inter-
4076         preted  as a class containing a range followed by two other characters.         preted as a class containing a range followed by two other  characters.
4077         The octal or hexadecimal representation of "]" can also be used to  end         The  octal or hexadecimal representation of "]" can also be used to end
4078         a range.         a range.
4079    
4080         Ranges  operate in the collating sequence of character values. They can         Ranges operate in the collating sequence of character values. They  can
4081         also  be  used  for  characters  specified  numerically,  for   example         also   be  used  for  characters  specified  numerically,  for  example
4082         [\000-\037].  In UTF-8 mode, ranges can include characters whose values         [\000-\037]. In UTF-8 mode, ranges can include characters whose  values
4083         are greater than 255, for example [\x{100}-\x{2ff}].         are greater than 255, for example [\x{100}-\x{2ff}].
4084    
4085         If a range that includes letters is used when caseless matching is set,         If a range that includes letters is used when caseless matching is set,
4086         it matches the letters in either case. For example, [W-c] is equivalent         it matches the letters in either case. For example, [W-c] is equivalent
4087         to [][\\^_`wxyzabc], matched caselessly,  and  in  non-UTF-8  mode,  if         to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if
4088         character  tables  for  a French locale are in use, [\xc8-\xcb] matches         character tables for a French locale are in  use,  [\xc8-\xcb]  matches
4089         accented E characters in both cases. In UTF-8 mode, PCRE  supports  the         accented  E  characters in both cases. In UTF-8 mode, PCRE supports the
4090         concept  of  case for characters with values greater than 128 only when         concept of case for characters with values greater than 128  only  when
4091         it is compiled with Unicode property support.         it is compiled with Unicode property support.
4092    
4093         The character types \d, \D, \h, \H, \p, \P, \s, \S, \v, \V, \w, and  \W         The  character escape sequences \d, \D, \h, \H, \p, \P, \s, \S, \v, \V,
4094         may  also appear in a character class, and add the characters that they         \w, and \W may appear in a character class, and add the characters that
4095         match to the class. For example,  [\dABCDEF]  matches  any  hexadecimal         they  match to the class. For example, [\dABCDEF] matches any hexadeci-
4096         digit.  A circumflex can conveniently be used with the upper case char-         mal digit. In UTF-8 mode, the PCRE_UCP option affects the  meanings  of
4097         acter types to specify a more restricted set  of  characters  than  the         \d,  \s,  \w  and  their upper case partners, just as it does when they
4098         matching  lower  case  type.  For example, the class [^\W_] matches any         appear outside a character class, as described in the section  entitled
4099         letter or digit, but not underscore.         "Generic character types" above. The escape sequence \b has a different
4100           meaning inside a character class; it matches the  backspace  character.
4101         The only metacharacters that are recognized in  character  classes  are         The  sequences  \B,  \N,  \R, and \X are not special inside a character
4102         backslash,  hyphen  (only  where  it can be interpreted as specifying a         class. Like any other unrecognized escape sequences, they  are  treated
4103         range), circumflex (only at the start), opening  square  bracket  (only         as  the literal characters "B", "N", "R", and "X" by default, but cause
4104         when  it can be interpreted as introducing a POSIX class name - see the         an error if the PCRE_EXTRA option is set.
4105         next section), and the terminating  closing  square  bracket.  However,  
4106           A circumflex can conveniently be used with  the  upper  case  character
4107           types  to specify a more restricted set of characters than the matching
4108           lower case type.  For example, the class [^\W_] matches any  letter  or
4109           digit, but not underscore, whereas [\w] includes underscore. A positive
4110           character class should be read as "something OR something OR ..." and a
4111           negative class as "NOT something AND NOT something AND NOT ...".
4112    
4113           The  only  metacharacters  that are recognized in character classes are
4114           backslash, hyphen (only where it can be  interpreted  as  specifying  a
4115           range),  circumflex  (only  at the start), opening square bracket (only
4116           when it can be interpreted as introducing a POSIX class name - see  the
4117           next  section),  and  the  terminating closing square bracket. However,
4118         escaping other non-alphanumeric characters does no harm.         escaping other non-alphanumeric characters does no harm.
4119    
4120    
4121  POSIX CHARACTER CLASSES  POSIX CHARACTER CLASSES
4122    
4123         Perl supports the POSIX notation for character classes. This uses names         Perl supports the POSIX notation for character classes. This uses names
4124         enclosed by [: and :] within the enclosing square brackets.  PCRE  also         enclosed  by  [: and :] within the enclosing square brackets. PCRE also
4125         supports this notation. For example,         supports this notation. For example,
4126    
4127           [01[:alpha:]%]           [01[:alpha:]%]
# Line 4106  POSIX CHARACTER CLASSES Line 4144  POSIX CHARACTER CLASSES
4144           word     "word" characters (same as \w)           word     "word" characters (same as \w)
4145           xdigit   hexadecimal digits           xdigit   hexadecimal digits
4146    
4147         The "space" characters are HT (9), LF (10), VT (11), FF (12), CR  (13),         The  "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),
4148         and  space  (32). Notice that this list includes the VT character (code         and space (32). Notice that this list includes the VT  character  (code
4149         11). This makes "space" different to \s, which does not include VT (for         11). This makes "space" different to \s, which does not include VT (for
4150         Perl compatibility).         Perl compatibility).
4151    
4152         The  name  "word"  is  a Perl extension, and "blank" is a GNU extension         The name "word" is a Perl extension, and "blank"  is  a  GNU  extension
4153         from Perl 5.8. Another Perl extension is negation, which  is  indicated         from  Perl  5.8. Another Perl extension is negation, which is indicated
4154         by a ^ character after the colon. For example,         by a ^ character after the colon. For example,
4155    
4156           [12[:^digit:]]           [12[:^digit:]]
4157    
4158         matches  "1", "2", or any non-digit. PCRE (and Perl) also recognize the         matches "1", "2", or any non-digit. PCRE (and Perl) also recognize  the
4159         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but
4160         these are not supported, and an error is given if they are encountered.         these are not supported, and an error is given if they are encountered.
4161    
4162         By  default,  in UTF-8 mode, characters with values greater than 128 do         By default, in UTF-8 mode, characters with values greater than  128  do
4163         not match any of the POSIX character classes. However, if the  PCRE_UCP         not  match any of the POSIX character classes. However, if the PCRE_UCP
4164         option  is passed to pcre_compile(), some of the classes are changed so         option is passed to pcre_compile(), some of the classes are changed  so
4165         that Unicode character properties are used. This is achieved by replac-         that Unicode character properties are used. This is achieved by replac-
4166         ing the POSIX classes by other sequences, as follows:         ing the POSIX classes by other sequences, as follows:
4167    
# Line 4136  POSIX CHARACTER CLASSES Line 4174  POSIX CHARACTER CLASSES
4174           [:upper:]  becomes  \p{Lu}           [:upper:]  becomes  \p{Lu}
4175           [:word:]   becomes  \p{Xwd}           [:word:]   becomes  \p{Xwd}
4176    
4177         Negated  versions,  such  as [:^alpha:] use \P instead of \p. The other         Negated versions, such as [:^alpha:] use \P instead of  \p.  The  other
4178         POSIX classes are unchanged, and match only characters with code points         POSIX classes are unchanged, and match only characters with code points
4179         less than 128.         less than 128.
4180    
4181    
4182  VERTICAL BAR  VERTICAL BAR
4183    
4184         Vertical  bar characters are used to separate alternative patterns. For         Vertical bar characters are used to separate alternative patterns.  For
4185         example, the pattern         example, the pattern
4186    
4187           gilbert|sullivan           gilbert|sullivan
4188    
4189         matches either "gilbert" or "sullivan". Any number of alternatives  may         matches  either "gilbert" or "sullivan". Any number of alternatives may
4190         appear,  and  an  empty  alternative  is  permitted (matching the empty         appear, and an empty  alternative  is  permitted  (matching  the  empty
4191         string). The matching process tries each alternative in turn, from left         string). The matching process tries each alternative in turn, from left
4192         to  right, and the first one that succeeds is used. If the alternatives         to right, and the first one that succeeds is used. If the  alternatives
4193         are within a subpattern (defined below), "succeeds" means matching  the         are  within a subpattern (defined below), "succeeds" means matching the
4194         rest of the main pattern as well as the alternative in the subpattern.         rest of the main pattern as well as the alternative in the subpattern.
4195    
4196    
4197  INTERNAL OPTION SETTING  INTERNAL OPTION SETTING
4198    
4199         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and         The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and
4200         PCRE_EXTENDED options (which are Perl-compatible) can be  changed  from         PCRE_EXTENDED  options  (which are Perl-compatible) can be changed from
4201         within  the  pattern  by  a  sequence  of  Perl option letters enclosed         within the pattern by  a  sequence  of  Perl  option  letters  enclosed
4202         between "(?" and ")".  The option letters are         between "(?" and ")".  The option letters are
4203    
4204           i  for PCRE_CASELESS           i  for PCRE_CASELESS
# Line 4170  INTERNAL OPTION SETTING Line 4208  INTERNAL OPTION SETTING
4208    
4209         For example, (?im) sets caseless, multiline matching. It is also possi-         For example, (?im) sets caseless, multiline matching. It is also possi-
4210         ble to unset these options by preceding the letter with a hyphen, and a         ble to unset these options by preceding the letter with a hyphen, and a
4211         combined setting and unsetting such as (?im-sx), which sets  PCRE_CASE-         combined  setting and unsetting such as (?im-sx), which sets PCRE_CASE-
4212         LESS  and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,         LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and  PCRE_EXTENDED,
4213         is also permitted. If a  letter  appears  both  before  and  after  the         is  also  permitted.  If  a  letter  appears  both before and after the
4214         hyphen, the option is unset.         hyphen, the option is unset.
4215    
4216         The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA         The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA
4217         can be changed in the same way as the Perl-compatible options by  using         can  be changed in the same way as the Perl-compatible options by using
4218         the characters J, U and X respectively.         the characters J, U and X respectively.
4219    
4220         When  one  of  these  option  changes occurs at top level (that is, not         When one of these option changes occurs at  top  level  (that  is,  not
4221         inside subpattern parentheses), the change applies to the remainder  of         inside  subpattern parentheses), the change applies to the remainder of
4222         the pattern that follows. If the change is placed right at the start of         the pattern that follows. If the change is placed right at the start of
4223         a pattern, PCRE extracts it into the global options (and it will there-         a pattern, PCRE extracts it into the global options (and it will there-
4224         fore show up in data extracted by the pcre_fullinfo() function).         fore show up in data extracted by the pcre_fullinfo() function).
4225    
4226         An  option  change  within a subpattern (see below for a description of         An option change within a subpattern (see below for  a  description  of
4227         subpatterns) affects only that part of the subpattern that follows  it,         subpatterns)  affects only that part of the subpattern that follows it,
4228         so         so
4229    
4230           (a(?i)b)c           (a(?i)b)c
4231    
4232         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not
4233         used).  By this means, options can be made to have  different  settings         used).   By  this means, options can be made to have different settings
4234         in  different parts of the pattern. Any changes made in one alternative         in different parts of the pattern. Any changes made in one  alternative
4235         do carry on into subsequent branches within the  same  subpattern.  For         do  carry  on  into subsequent branches within the same subpattern. For
4236         example,         example,
4237    
4238           (a(?i)b|c)           (a(?i)b|c)
4239    
4240         matches  "ab",  "aB",  "c",  and "C", even though when matching "C" the         matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the
4241         first branch is abandoned before the option setting.  This  is  because         first  branch  is  abandoned before the option setting. This is because
4242         the  effects  of option settings happen at compile time. There would be         the effects of option settings happen at compile time. There  would  be
4243         some very weird behaviour otherwise.         some very weird behaviour otherwise.
4244    
4245         Note: There are other PCRE-specific options that  can  be  set  by  the         Note:  There  are  other  PCRE-specific  options that can be set by the
4246         application  when  the  compile  or match functions are called. In some         application when the compile or match functions  are  called.  In  some
4247         cases the pattern can contain special leading sequences such as (*CRLF)         cases the pattern can contain special leading sequences such as (*CRLF)
4248         to  override  what  the application has set or what has been defaulted.         to override what the application has set or what  has  been  defaulted.
4249         Details are given in the section entitled  "Newline  sequences"  above.         Details  are  given  in the section entitled "Newline sequences" above.
4250         There  are  also  the  (*UTF8) and (*UCP) leading sequences that can be         There are also the (*UTF8) and (*UCP) leading  sequences  that  can  be
4251         used to set UTF-8 and Unicode property modes; they  are  equivalent  to         used  to  set  UTF-8 and Unicode property modes; they are equivalent to
4252         setting the PCRE_UTF8 and the PCRE_UCP options, respectively.         setting the PCRE_UTF8 and the PCRE_UCP options, respectively.
4253    
4254    
# Line 4223  SUBPATTERNS Line 4261  SUBPATTERNS
4261    
4262           cat(aract|erpillar|)           cat(aract|erpillar|)
4263    
4264         matches "cataract", "caterpillar", or "cat". Without  the  parentheses,         matches  "cataract",  "caterpillar", or "cat". Without the parentheses,
4265         it would match "cataract", "erpillar" or an empty string.         it would match "cataract", "erpillar" or an empty string.
4266    
4267         2.  It  sets  up  the  subpattern as a capturing subpattern. This means         2. It sets up the subpattern as  a  capturing  subpattern.  This  means
4268         that, when the whole pattern  matches,  that  portion  of  the  subject         that,  when  the  whole  pattern  matches,  that portion of the subject
4269         string that matched the subpattern is passed back to the caller via the         string that matched the subpattern is passed back to the caller via the
4270         ovector argument of pcre_exec(). Opening parentheses are  counted  from         ovector  argument  of pcre_exec(). Opening parentheses are counted from
4271         left  to  right  (starting  from 1) to obtain numbers for the capturing         left to right (starting from 1) to obtain  numbers  for  the  capturing
4272         subpatterns. For example, if the  string  "the  red  king"  is  matched         subpatterns.  For  example,  if  the  string  "the red king" is matched
4273         against the pattern         against the pattern
4274    
4275           the ((red|white) (king|queen))           the ((red|white) (king|queen))
# Line 4239  SUBPATTERNS Line 4277  SUBPATTERNS
4277         the captured substrings are "red king", "red", and "king", and are num-         the captured substrings are "red king", "red", and "king", and are num-
4278         bered 1, 2, and 3, respectively.         bered 1, 2, and 3, respectively.
4279    
4280         The fact that plain parentheses fulfil  two  functions  is  not  always         The  fact  that  plain  parentheses  fulfil two functions is not always
4281         helpful.   There are often times when a grouping subpattern is required         helpful.  There are often times when a grouping subpattern is  required
4282         without a capturing requirement. If an opening parenthesis is  followed         without  a capturing requirement. If an opening parenthesis is followed
4283         by  a question mark and a colon, the subpattern does not do any captur-         by a question mark and a colon, the subpattern does not do any  captur-
4284         ing, and is not counted when computing the  number  of  any  subsequent         ing,  and  is  not  counted when computing the number of any subsequent
4285         capturing  subpatterns. For example, if the string "the white queen" is         capturing subpatterns. For example, if the string "the white queen"  is
4286         matched against the pattern         matched against the pattern
4287    
4288           the ((?:red|white) (king|queen))           the ((?:red|white) (king|queen))
# Line 4252  SUBPATTERNS Line 4290  SUBPATTERNS
4290         the captured substrings are "white queen" and "queen", and are numbered         the captured substrings are "white queen" and "queen", and are numbered
4291         1 and 2. The maximum number of capturing subpatterns is 65535.         1 and 2. The maximum number of capturing subpatterns is 65535.
4292    
4293         As  a  convenient shorthand, if any option settings are required at the         As a convenient shorthand, if any option settings are required  at  the
4294         start of a non-capturing subpattern,  the  option  letters  may  appear         start  of  a  non-capturing  subpattern,  the option letters may appear
4295         between the "?" and the ":". Thus the two patterns         between the "?" and the ":". Thus the two patterns
4296    
4297           (?i:saturday|sunday)           (?i:saturday|sunday)
4298           (?:(?i)saturday|sunday)           (?:(?i)saturday|sunday)
4299    
4300         match exactly the same set of strings. Because alternative branches are         match exactly the same set of strings. Because alternative branches are
4301         tried from left to right, and options are not reset until  the  end  of         tried  from  left  to right, and options are not reset until the end of
4302         the  subpattern is reached, an option setting in one branch does affect         the subpattern is reached, an option setting in one branch does  affect
4303         subsequent branches, so the above patterns match "SUNDAY"  as  well  as         subsequent  branches,  so  the above patterns match "SUNDAY" as well as
4304         "Saturday".         "Saturday".
4305    
4306    
4307  DUPLICATE SUBPATTERN NUMBERS  DUPLICATE SUBPATTERN NUMBERS
4308    
4309         Perl 5.10 introduced a feature whereby each alternative in a subpattern         Perl 5.10 introduced a feature whereby each alternative in a subpattern
4310         uses the same numbers for its capturing parentheses. Such a  subpattern         uses  the same numbers for its capturing parentheses. Such a subpattern
4311         starts  with (?| and is itself a non-capturing subpattern. For example,         starts with (?| and is itself a non-capturing subpattern. For  example,
4312         consider this pattern:         consider this pattern:
4313    
4314           (?|(Sat)ur|(Sun))day           (?|(Sat)ur|(Sun))day
4315    
4316         Because the two alternatives are inside a (?| group, both sets of  cap-         Because  the two alternatives are inside a (?| group, both sets of cap-
4317         turing  parentheses  are  numbered one. Thus, when the pattern matches,         turing parentheses are numbered one. Thus, when  the  pattern  matches,
4318         you can look at captured substring number  one,  whichever  alternative         you  can  look  at captured substring number one, whichever alternative
4319         matched.  This  construct  is useful when you want to capture part, but         matched. This construct is useful when you want to  capture  part,  but
4320         not all, of one of a number of alternatives. Inside a (?| group, paren-         not all, of one of a number of alternatives. Inside a (?| group, paren-
4321         theses  are  numbered as usual, but the number is reset at the start of         theses are numbered as usual, but the number is reset at the  start  of
4322         each branch. The numbers of any capturing parentheses that  follow  the         each  branch.  The numbers of any capturing parentheses that follow the
4323         subpattern  start after the highest number used in any branch. The fol-         subpattern start after the highest number used in any branch. The  fol-
4324         lowing example is taken from the Perl documentation. The numbers under-         lowing example is taken from the Perl documentation. The numbers under-
4325         neath show in which buffer the captured content will be stored.         neath show in which buffer the captured content will be stored.
4326    
# Line 4290  DUPLICATE SUBPATTERN NUMBERS Line 4328  DUPLICATE SUBPATTERN NUMBERS
4328           / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x           / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
4329           # 1            2         2  3        2     3     4           # 1            2         2  3        2     3     4
4330    
4331         A  back  reference  to a numbered subpattern uses the most recent value         A back reference to a numbered subpattern uses the  most  recent  value
4332         that is set for that number by any subpattern.  The  following  pattern         that  is  set  for that number by any subpattern. The following pattern
4333         matches "abcabc" or "defdef":         matches "abcabc" or "defdef":
4334    
4335           /(?|(abc)|(def))\1/           /(?|(abc)|(def))\1/
4336    
4337         In  contrast, a recursive or "subroutine" call to a numbered subpattern         In contrast, a recursive or "subroutine" call to a numbered  subpattern
4338         always refers to the first one in the pattern with  the  given  number.         always  refers  to  the first one in the pattern with the given number.
4339         The following pattern matches "abcabc" or "defabc":         The following pattern matches "abcabc" or "defabc":
4340    
4341           /(?|(abc)|(def))(?1)/           /(?|(abc)|(def))(?1)/
4342    
4343         If  a condition test for a subpattern's having matched refers to a non-         If a condition test for a subpattern's having matched refers to a  non-
4344         unique number, the test is true if any of the subpatterns of that  num-         unique  number, the test is true if any of the subpatterns of that num-
4345         ber have matched.         ber have matched.
4346    
4347         An  alternative approach to using this "branch reset" feature is to use         An alternative approach to using this "branch reset" feature is to  use
4348         duplicate named subpatterns, as described in the next section.         duplicate named subpatterns, as described in the next section.
4349    
4350    
4351  NAMED SUBPATTERNS  NAMED SUBPATTERNS
4352    
4353         Identifying capturing parentheses by number is simple, but  it  can  be         Identifying  capturing  parentheses  by number is simple, but it can be
4354         very  hard  to keep track of the numbers in complicated regular expres-         very hard to keep track of the numbers in complicated  regular  expres-
4355         sions. Furthermore, if an  expression  is  modified,  the  numbers  may         sions.  Furthermore,  if  an  expression  is  modified, the numbers may
4356         change.  To help with this difficulty, PCRE supports the naming of sub-         change. To help with this difficulty, PCRE supports the naming of  sub-
4357         patterns. This feature was not added to Perl until release 5.10. Python         patterns. This feature was not added to Perl until release 5.10. Python
4358         had  the  feature earlier, and PCRE introduced it at release 4.0, using         had the feature earlier, and PCRE introduced it at release  4.0,  using
4359         the Python syntax. PCRE now supports both the Perl and the Python  syn-         the  Python syntax. PCRE now supports both the Perl and the Python syn-
4360         tax.  Perl  allows  identically  numbered subpatterns to have different         tax. Perl allows identically numbered  subpatterns  to  have  different
4361         names, but PCRE does not.         names, but PCRE does not.
4362    
4363         In PCRE, a subpattern can be named in one of three  ways:  (?<name>...)         In  PCRE,  a subpattern can be named in one of three ways: (?<name>...)
4364         or  (?'name'...)  as in Perl, or (?P<name>...) as in Python. References         or (?'name'...) as in Perl, or (?P<name>...) as in  Python.  References
4365         to capturing parentheses from other parts of the pattern, such as  back         to  capturing parentheses from other parts of the pattern, such as back
4366         references,  recursion,  and conditions, can be made by name as well as         references, recursion, and conditions, can be made by name as  well  as
4367         by number.         by number.
4368    
4369         Names consist of up to  32  alphanumeric  characters  and  underscores.         Names  consist  of  up  to  32 alphanumeric characters and underscores.
4370         Named  capturing  parentheses  are  still  allocated numbers as well as         Named capturing parentheses are still  allocated  numbers  as  well  as
4371         names, exactly as if the names were not present. The PCRE API  provides         names,  exactly as if the names were not present. The PCRE API provides
4372         function calls for extracting the name-to-number translation table from         function calls for extracting the name-to-number translation table from
4373         a compiled pattern. There is also a convenience function for extracting         a compiled pattern. There is also a convenience function for extracting
4374         a captured substring by name.         a captured substring by name.
4375    
4376         By  default, a name must be unique within a pattern, but it is possible         By default, a name must be unique within a pattern, but it is  possible
4377         to relax this constraint by setting the PCRE_DUPNAMES option at compile         to relax this constraint by setting the PCRE_DUPNAMES option at compile
4378         time.  (Duplicate  names are also always permitted for subpatterns with         time. (Duplicate names are also always permitted for  subpatterns  with
4379         the same number, set up as described in the previous  section.)  Dupli-         the  same  number, set up as described in the previous section.) Dupli-
4380         cate  names  can  be useful for patterns where only one instance of the         cate names can be useful for patterns where only one  instance  of  the
4381         named parentheses can match. Suppose you want to match the  name  of  a         named  parentheses  can  match. Suppose you want to match the name of a
4382         weekday,  either as a 3-letter abbreviation or as the full name, and in         weekday, either as a 3-letter abbreviation or as the full name, and  in
4383         both cases you want to extract the abbreviation. This pattern (ignoring         both cases you want to extract the abbreviation. This pattern (ignoring
4384         the line breaks) does the job:         the line breaks) does the job:
4385    
# Line 4351  NAMED SUBPATTERNS Line 4389  NAMED SUBPATTERNS
4389           (?<DN>Thu)(?:rsday)?|           (?<DN>Thu)(?:rsday)?|
4390           (?<DN>Sat)(?:urday)?           (?<DN>Sat)(?:urday)?
4391    
4392         There  are  five capturing substrings, but only one is ever set after a         There are five capturing substrings, but only one is ever set  after  a
4393         match.  (An alternative way of solving this problem is to use a "branch         match.  (An alternative way of solving this problem is to use a "branch
4394         reset" subpattern, as described in the previous section.)         reset" subpattern, as described in the previous section.)
4395    
4396         The  convenience  function  for extracting the data by name returns the         The convenience function for extracting the data by  name  returns  the
4397         substring for the first (and in this example, the only)  subpattern  of         substring  for  the first (and in this example, the only) subpattern of
4398         that  name  that  matched.  This saves searching to find which numbered         that name that matched. This saves searching  to  find  which  numbered
4399         subpattern it was.         subpattern it was.
4400    
4401         If you make a back reference to  a  non-unique  named  subpattern  from         If  you  make  a  back  reference to a non-unique named subpattern from
4402         elsewhere  in the pattern, the one that corresponds to the first occur-         elsewhere in the pattern, the one that corresponds to the first  occur-
4403         rence of the name is used. In the absence of duplicate numbers (see the         rence of the name is used. In the absence of duplicate numbers (see the
4404         previous  section) this is the one with the lowest number. If you use a         previous section) this is the one with the lowest number. If you use  a
4405         named reference in a condition test (see the section  about  conditions         named  reference  in a condition test (see the section about conditions
4406         below),  either  to check whether a subpattern has matched, or to check         below), either to check whether a subpattern has matched, or  to  check
4407         for recursion, all subpatterns with the same name are  tested.  If  the         for  recursion,  all  subpatterns with the same name are tested. If the
4408         condition  is  true for any one of them, the overall condition is true.         condition is true for any one of them, the overall condition  is  true.
4409         This is the same behaviour as testing by number. For further details of         This is the same behaviour as testing by number. For further details of
4410         the interfaces for handling named subpatterns, see the pcreapi documen-         the interfaces for handling named subpatterns, see the pcreapi documen-
4411         tation.         tation.
4412    
4413         Warning: You cannot use different names to distinguish between two sub-         Warning: You cannot use different names to distinguish between two sub-
4414         patterns  with  the same number because PCRE uses only the numbers when         patterns with the same number because PCRE uses only the  numbers  when
4415         matching. For this reason, an error is given at compile time if differ-         matching. For this reason, an error is given at compile time if differ-
4416         ent  names  are given to subpatterns with the same number. However, you         ent names are given to subpatterns with the same number.  However,  you
4417         can give the same name to subpatterns with the same number,  even  when         can  give  the same name to subpatterns with the same number, even when
4418         PCRE_DUPNAMES is not set.         PCRE_DUPNAMES is not set.
4419    
4420    
4421  REPETITION  REPETITION
4422    
4423         Repetition  is  specified  by  quantifiers, which can follow any of the         Repetition is specified by quantifiers, which can  follow  any  of  the
4424         following items:         following items:
4425    
4426           a literal data character           a literal data character
# Line 4396  REPETITION Line 4434  REPETITION
4434           a parenthesized subpattern (unless it is an assertion)           a parenthesized subpattern (unless it is an assertion)
4435           a recursive or "subroutine" call to a subpattern           a recursive or "subroutine" call to a subpattern
4436    
4437         The general repetition quantifier specifies a minimum and maximum  num-         The  general repetition quantifier specifies a minimum and maximum num-
4438         ber  of  permitted matches, by giving the two numbers in curly brackets         ber of permitted matches, by giving the two numbers in  curly  brackets
4439         (braces), separated by a comma. The numbers must be  less  than  65536,         (braces),  separated  by  a comma. The numbers must be less than 65536,
4440         and the first must be less than or equal to the second. For example:         and the first must be less than or equal to the second. For example:
4441    
4442           z{2,4}           z{2,4}
4443    
4444         matches  "zz",  "zzz",  or  "zzzz". A closing brace on its own is not a         matches "zz", "zzz", or "zzzz". A closing brace on its  own  is  not  a
4445         special character. If the second number is omitted, but  the  comma  is         special  character.  If  the second number is omitted, but the comma is
4446         present,  there  is  no upper limit; if the second number and the comma         present, there is no upper limit; if the second number  and  the  comma
4447         are both omitted, the quantifier specifies an exact number of  required         are  both omitted, the quantifier specifies an exact number of required
4448         matches. Thus         matches. Thus
4449    
4450           [aeiou]{3,}           [aeiou]{3,}
# Line 4415  REPETITION Line 4453  REPETITION
4453    
4454           \d{8}           \d{8}
4455    
4456         matches  exactly  8  digits. An opening curly bracket that appears in a         matches exactly 8 digits. An opening curly bracket that  appears  in  a
4457         position where a quantifier is not allowed, or one that does not  match         position  where a quantifier is not allowed, or one that does not match
4458         the  syntax of a quantifier, is taken as a literal character. For exam-         the syntax of a quantifier, is taken as a literal character. For  exam-
4459         ple, {,6} is not a quantifier, but a literal string of four characters.         ple, {,6} is not a quantifier, but a literal string of four characters.
4460    
4461         In UTF-8 mode, quantifiers apply to UTF-8  characters  rather  than  to         In  UTF-8  mode,  quantifiers  apply to UTF-8 characters rather than to
4462         individual bytes. Thus, for example, \x{100}{2} matches two UTF-8 char-         individual bytes. Thus, for example, \x{100}{2} matches two UTF-8 char-
4463         acters, each of which is represented by a two-byte sequence. Similarly,         acters, each of which is represented by a two-byte sequence. Similarly,
4464         when Unicode property support is available, \X{3} matches three Unicode         when Unicode property support is available, \X{3} matches three Unicode
4465         extended sequences, each of which may be several bytes long  (and  they         extended  sequences,  each of which may be several bytes long (and they
4466         may be of different lengths).         may be of different lengths).
4467    
4468         The quantifier {0} is permitted, causing the expression to behave as if         The quantifier {0} is permitted, causing the expression to behave as if
4469         the previous item and the quantifier were not present. This may be use-         the previous item and the quantifier were not present. This may be use-
4470         ful  for  subpatterns that are referenced as subroutines from elsewhere         ful for subpatterns that are referenced as subroutines  from  elsewhere
4471         in the pattern (but see also the section entitled "Defining subpatterns         in the pattern (but see also the section entitled "Defining subpatterns
4472         for  use  by  reference only" below). Items other than subpatterns that         for use by reference only" below). Items other  than  subpatterns  that
4473         have a {0} quantifier are omitted from the compiled pattern.         have a {0} quantifier are omitted from the compiled pattern.
4474    
4475         For convenience, the three most common quantifiers have  single-charac-         For  convenience, the three most common quantifiers have single-charac-
4476         ter abbreviations:         ter abbreviations:
4477    
4478           *    is equivalent to {0,}           *    is equivalent to {0,}
4479           +    is equivalent to {1,}           +    is equivalent to {1,}
4480           ?    is equivalent to {0,1}           ?    is equivalent to {0,1}
4481    
4482         It  is  possible  to construct infinite loops by following a subpattern         It is possible to construct infinite loops by  following  a  subpattern
4483         that can match no characters with a quantifier that has no upper limit,         that can match no characters with a quantifier that has no upper limit,
4484         for example:         for example:
4485    
4486           (a?)*           (a?)*
4487    
4488         Earlier versions of Perl and PCRE used to give an error at compile time         Earlier versions of Perl and PCRE used to give an error at compile time
4489         for such patterns. However, because there are cases where this  can  be         for  such  patterns. However, because there are cases where this can be
4490         useful,  such  patterns  are now accepted, but if any repetition of the         useful, such patterns are now accepted, but if any  repetition  of  the
4491         subpattern does in fact match no characters, the loop is forcibly  bro-         subpattern  does in fact match no characters, the loop is forcibly bro-
4492         ken.         ken.
4493    
4494         By  default,  the quantifiers are "greedy", that is, they match as much         By default, the quantifiers are "greedy", that is, they match  as  much
4495         as possible (up to the maximum  number  of  permitted  times),  without         as  possible  (up  to  the  maximum number of permitted times), without
4496         causing  the  rest of the pattern to fail. The classic example of where         causing the rest of the pattern to fail. The classic example  of  where
4497         this gives problems is in trying to match comments in C programs. These         this gives problems is in trying to match comments in C programs. These
4498         appear  between  /*  and  */ and within the comment, individual * and /         appear between /* and */ and within the comment,  individual  *  and  /
4499         characters may appear. An attempt to match C comments by  applying  the         characters  may  appear. An attempt to match C comments by applying the
4500         pattern         pattern
4501    
4502           /\*.*\*/           /\*.*\*/
# Line 4467  REPETITION Line 4505  REPETITION
4505    
4506           /* first comment */  not comment  /* second comment */           /* first comment */  not comment  /* second comment */
4507    
4508         fails,  because it matches the entire string owing to the greediness of         fails, because it matches the entire string owing to the greediness  of
4509         the .*  item.         the .*  item.
4510    
4511         However, if a quantifier is followed by a question mark, it  ceases  to         However,  if  a quantifier is followed by a question mark, it ceases to
4512         be greedy, and instead matches the minimum number of times possible, so         be greedy, and instead matches the minimum number of times possible, so
4513         the pattern         the pattern
4514    
4515           /\*.*?\*/           /\*.*?\*/
4516    
4517         does the right thing with the C comments. The meaning  of  the  various         does  the  right  thing with the C comments. The meaning of the various
4518         quantifiers  is  not  otherwise  changed,  just the preferred number of         quantifiers is not otherwise changed,  just  the  preferred  number  of
4519         matches.  Do not confuse this use of question mark with its  use  as  a         matches.   Do  not  confuse this use of question mark with its use as a
4520         quantifier  in its own right. Because it has two uses, it can sometimes         quantifier in its own right. Because it has two uses, it can  sometimes
4521         appear doubled, as in         appear doubled, as in
4522    
4523           \d??\d           \d??\d
# Line 4487  REPETITION Line 4525  REPETITION
4525         which matches one digit by preference, but can match two if that is the         which matches one digit by preference, but can match two if that is the
4526         only way the rest of the pattern matches.         only way the rest of the pattern matches.
4527    
4528         If  the PCRE_UNGREEDY option is set (an option that is not available in         If the PCRE_UNGREEDY option is set (an option that is not available  in
4529         Perl), the quantifiers are not greedy by default, but  individual  ones         Perl),  the  quantifiers are not greedy by default, but individual ones
4530         can  be  made  greedy  by following them with a question mark. In other         can be made greedy by following them with a  question  mark.  In  other
4531         words, it inverts the default behaviour.         words, it inverts the default behaviour.
4532    
4533         When a parenthesized subpattern is quantified  with  a  minimum  repeat         When  a  parenthesized  subpattern  is quantified with a minimum repeat
4534         count  that is greater than 1 or with a limited maximum, more memory is         count that is greater than 1 or with a limited maximum, more memory  is
4535         required for the compiled pattern, in proportion to  the  size  of  the         required  for  the  compiled  pattern, in proportion to the size of the
4536         minimum or maximum.         minimum or maximum.
4537    
4538         If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-         If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-
4539         alent to Perl's /s) is set, thus allowing the dot  to  match  newlines,         alent  to  Perl's  /s) is set, thus allowing the dot to match newlines,
4540         the  pattern  is  implicitly anchored, because whatever follows will be         the pattern is implicitly anchored, because whatever  follows  will  be
4541         tried against every character position in the subject string, so  there         tried  against every character position in the subject string, so there
4542         is  no  point  in  retrying the overall match at any position after the         is no point in retrying the overall match at  any  position  after  the
4543         first. PCRE normally treats such a pattern as though it  were  preceded         first.  PCRE  normally treats such a pattern as though it were preceded
4544         by \A.         by \A.
4545    
4546         In  cases  where  it  is known that the subject string contains no new-         In cases where it is known that the subject  string  contains  no  new-
4547         lines, it is worth setting PCRE_DOTALL in order to  obtain  this  opti-         lines,  it  is  worth setting PCRE_DOTALL in order to obtain this opti-
4548         mization, or alternatively using ^ to indicate anchoring explicitly.         mization, or alternatively using ^ to indicate anchoring explicitly.
4549    
4550         However,  there is one situation where the optimization cannot be used.         However, there is one situation where the optimization cannot be  used.
4551         When .*  is inside capturing parentheses that are the subject of a back         When .*  is inside capturing parentheses that are the subject of a back
4552         reference elsewhere in the pattern, a match at the start may fail where         reference elsewhere in the pattern, a match at the start may fail where
4553         a later one succeeds. Consider, for example:         a later one succeeds. Consider, for example:
4554    
4555           (.*)abc\1           (.*)abc\1
4556    
4557         If the subject is "xyz123abc123" the match point is the fourth  charac-         If  the subject is "xyz123abc123" the match point is the fourth charac-
4558         ter. For this reason, such a pattern is not implicitly anchored.         ter. For this reason, such a pattern is not implicitly anchored.
4559    
4560         When a capturing subpattern is repeated, the value captured is the sub-         When a capturing subpattern is repeated, the value captured is the sub-
# Line 4525  REPETITION Line 4563  REPETITION
4563           (tweedle[dume]{3}\s*)+           (tweedle[dume]{3}\s*)+
4564    
4565         has matched "tweedledum tweedledee" the value of the captured substring         has matched "tweedledum tweedledee" the value of the captured substring
4566         is  "tweedledee".  However,  if there are nested capturing subpatterns,         is "tweedledee". However, if there are  nested  capturing  subpatterns,
4567         the corresponding captured values may have been set in previous  itera-         the  corresponding captured values may have been set in previous itera-
4568         tions. For example, after         tions. For example, after
4569    
4570           /(a|(b))+/           /(a|(b))+/
# Line 4536  REPETITION Line 4574  REPETITION
4574    
4575  ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS  ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS
4576    
4577         With  both  maximizing ("greedy") and minimizing ("ungreedy" or "lazy")         With both maximizing ("greedy") and minimizing ("ungreedy"  or  "lazy")
4578         repetition, failure of what follows normally causes the  repeated  item         repetition,  failure  of what follows normally causes the repeated item
4579         to  be  re-evaluated to see if a different number of repeats allows the         to be re-evaluated to see if a different number of repeats  allows  the
4580         rest of the pattern to match. Sometimes it is useful to  prevent  this,         rest  of  the pattern to match. Sometimes it is useful to prevent this,
4581         either  to  change the nature of the match, or to cause it fail earlier         either to change the nature of the match, or to cause it  fail  earlier
4582         than it otherwise might, when the author of the pattern knows there  is         than  it otherwise might, when the author of the pattern knows there is
4583         no point in carrying on.         no point in carrying on.
4584    
4585         Consider,  for  example, the pattern \d+foo when applied to the subject         Consider, for example, the pattern \d+foo when applied to  the  subject
4586         line         line
4587    
4588           123456bar           123456bar
4589    
4590         After matching all 6 digits and then failing to match "foo", the normal         After matching all 6 digits and then failing to match "foo", the normal
4591         action  of  the matcher is to try again with only 5 digits matching the         action of the matcher is to try again with only 5 digits  matching  the
4592         \d+ item, and then with  4,  and  so  on,  before  ultimately  failing.         \d+  item,  and  then  with  4,  and  so on, before ultimately failing.
4593         "Atomic  grouping"  (a  term taken from Jeffrey Friedl's book) provides         "Atomic grouping" (a term taken from Jeffrey  Friedl's  book)  provides
4594         the means for specifying that once a subpattern has matched, it is  not         the  means for specifying that once a subpattern has matched, it is not
4595         to be re-evaluated in this way.         to be re-evaluated in this way.
4596    
4597         If  we  use atomic grouping for the previous example, the matcher gives         If we use atomic grouping for the previous example, the  matcher  gives
4598         up immediately on failing to match "foo" the first time.  The  notation         up  immediately  on failing to match "foo" the first time. The notation
4599         is a kind of special parenthesis, starting with (?> as in this example:         is a kind of special parenthesis, starting with (?> as in this example:
4600    
4601           (?>\d+)foo           (?>\d+)foo
4602    
4603         This  kind  of  parenthesis "locks up" the  part of the pattern it con-         This kind of parenthesis "locks up" the  part of the  pattern  it  con-
4604         tains once it has matched, and a failure further into  the  pattern  is         tains  once  it  has matched, and a failure further into the pattern is
4605         prevented  from  backtracking into it. Backtracking past it to previous         prevented from backtracking into it. Backtracking past it  to  previous
4606         items, however, works as normal.         items, however, works as normal.
4607    
4608         An alternative description is that a subpattern of  this  type  matches         An  alternative  description  is that a subpattern of this type matches
4609         the  string  of  characters  that an identical standalone pattern would         the string of characters that an  identical  standalone  pattern  would
4610         match, if anchored at the current point in the subject string.         match, if anchored at the current point in the subject string.
4611    
4612         Atomic grouping subpatterns are not capturing subpatterns. Simple cases         Atomic grouping subpatterns are not capturing subpatterns. Simple cases
4613         such as the above example can be thought of as a maximizing repeat that         such as the above example can be thought of as a maximizing repeat that
4614         must swallow everything it can. So, while both \d+ and  \d+?  are  pre-         must  swallow  everything  it can. So, while both \d+ and \d+? are pre-
4615         pared  to  adjust  the number of digits they match in order to make the         pared to adjust the number of digits they match in order  to  make  the
4616         rest of the pattern match, (?>\d+) can only match an entire sequence of         rest of the pattern match, (?>\d+) can only match an entire sequence of
4617         digits.         digits.
4618    
4619         Atomic  groups in general can of course contain arbitrarily complicated         Atomic groups in general can of course contain arbitrarily  complicated
4620         subpatterns, and can be nested. However, when  the  subpattern  for  an         subpatterns,  and  can  be  nested. However, when the subpattern for an
4621         atomic group is just a single repeated item, as in the example above, a         atomic group is just a single repeated item, as in the example above, a
4622         simpler notation, called a "possessive quantifier" can  be  used.  This         simpler  notation,  called  a "possessive quantifier" can be used. This
4623         consists  of  an  additional  + character following a quantifier. Using         consists of an additional + character  following  a  quantifier.  Using
4624         this notation, the previous example can be rewritten as         this notation, the previous example can be rewritten as
4625    
4626           \d++foo           \d++foo
# Line 4592  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE Line 4630  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
4630    
4631           (abc|xyz){2,3}+           (abc|xyz){2,3}+
4632    
4633         Possessive   quantifiers   are   always  greedy;  the  setting  of  the         Possessive  quantifiers  are  always  greedy;  the   setting   of   the
4634         PCRE_UNGREEDY option is ignored. They are a convenient notation for the         PCRE_UNGREEDY option is ignored. They are a convenient notation for the
4635         simpler  forms  of atomic group. However, there is no difference in the         simpler forms of atomic group. However, there is no difference  in  the
4636         meaning of a possessive quantifier and  the  equivalent  atomic  group,         meaning  of  a  possessive  quantifier and the equivalent atomic group,
4637         though  there  may  be a performance difference; possessive quantifiers         though there may be a performance  difference;  possessive  quantifiers
4638         should be slightly faster.         should be slightly faster.
4639    
4640         The possessive quantifier syntax is an extension to the Perl  5.8  syn-         The  possessive  quantifier syntax is an extension to the Perl 5.8 syn-
4641         tax.   Jeffrey  Friedl  originated the idea (and the name) in the first         tax.  Jeffrey Friedl originated the idea (and the name)  in  the  first
4642         edition of his book. Mike McCloskey liked it, so implemented it when he         edition of his book. Mike McCloskey liked it, so implemented it when he
4643         built  Sun's Java package, and PCRE copied it from there. It ultimately         built Sun's Java package, and PCRE copied it from there. It  ultimately
4644         found its way into Perl at release 5.10.         found its way into Perl at release 5.10.
4645    
4646         PCRE has an optimization that automatically "possessifies" certain sim-         PCRE has an optimization that automatically "possessifies" certain sim-
4647         ple  pattern  constructs.  For  example, the sequence A+B is treated as         ple pattern constructs. For example, the sequence  A+B  is  treated  as
4648         A++B because there is no point in backtracking into a sequence  of  A's         A++B  because  there is no point in backtracking into a sequence of A's
4649         when B must follow.         when B must follow.
4650    
4651         When  a  pattern  contains an unlimited repeat inside a subpattern that         When a pattern contains an unlimited repeat inside  a  subpattern  that
4652         can itself be repeated an unlimited number of  times,  the  use  of  an         can  itself  be  repeated  an  unlimited number of times, the use of an
4653         atomic  group  is  the  only way to avoid some failing matches taking a         atomic group is the only way to avoid some  failing  matches  taking  a
4654         very long time indeed. The pattern         very long time indeed. The pattern
4655    
4656           (\D+|<\d+>)*[!?]           (\D+|<\d+>)*[!?]
4657    
4658         matches an unlimited number of substrings that either consist  of  non-         matches  an  unlimited number of substrings that either consist of non-
4659         digits,  or  digits  enclosed in <>, followed by either ! or ?. When it         digits, or digits enclosed in <>, followed by either ! or  ?.  When  it
4660         matches, it runs quickly. However, if it is applied to         matches, it runs quickly. However, if it is applied to
4661    
4662           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
4663    
4664         it takes a long time before reporting  failure.  This  is  because  the         it  takes  a  long  time  before reporting failure. This is because the
4665         string  can be divided between the internal \D+ repeat and the external         string can be divided between the internal \D+ repeat and the  external
4666         * repeat in a large number of ways, and all  have  to  be  tried.  (The         *  repeat  in  a  large  number of ways, and all have to be tried. (The
4667         example  uses  [!?]  rather than a single character at the end, because         example uses [!?] rather than a single character at  the  end,  because
4668         both PCRE and Perl have an optimization that allows  for  fast  failure         both  PCRE  and  Perl have an optimization that allows for fast failure
4669         when  a single character is used. They remember the last single charac-         when a single character is used. They remember the last single  charac-
4670         ter that is required for a match, and fail early if it is  not  present         ter  that  is required for a match, and fail early if it is not present
4671         in  the  string.)  If  the pattern is changed so that it uses an atomic         in the string.) If the pattern is changed so that  it  uses  an  atomic
4672         group, like this:         group, like this:
4673    
4674           ((?>\D+)|<\d+>)*[!?]           ((?>\D+)|<\d+>)*[!?]
# Line 4642  BACK REFERENCES Line 4680  BACK REFERENCES
4680    
4681         Outside a character class, a backslash followed by a digit greater than         Outside a character class, a backslash followed by a digit greater than
4682         0 (and possibly further digits) is a back reference to a capturing sub-         0 (and possibly further digits) is a back reference to a capturing sub-
4683         pattern earlier (that is, to its left) in the pattern,  provided  there         pattern  earlier  (that is, to its left) in the pattern, provided there
4684         have been that many previous capturing left parentheses.         have been that many previous capturing left parentheses.
4685    
4686         However, if the decimal number following the backslash is less than 10,         However, if the decimal number following the backslash is less than 10,
4687         it is always taken as a back reference, and causes  an  error  only  if         it  is  always  taken  as a back reference, and causes an error only if
4688         there  are  not that many capturing left parentheses in the entire pat-         there are not that many capturing left parentheses in the  entire  pat-
4689         tern. In other words, the parentheses that are referenced need  not  be         tern.  In  other words, the parentheses that are referenced need not be
4690         to  the left of the reference for numbers less than 10. A "forward back         to the left of the reference for numbers less than 10. A "forward  back
4691         reference" of this type can make sense when a  repetition  is  involved         reference"  of  this  type can make sense when a repetition is involved
4692         and  the  subpattern to the right has participated in an earlier itera-         and the subpattern to the right has participated in an  earlier  itera-
4693         tion.         tion.
4694    
4695         It is not possible to have a numerical "forward back  reference"  to  a         It  is  not  possible to have a numerical "forward back reference" to a
4696         subpattern  whose  number  is  10  or  more using this syntax because a         subpattern whose number is 10 or  more  using  this  syntax  because  a
4697         sequence such as \50 is interpreted as a character  defined  in  octal.         sequence  such  as  \50 is interpreted as a character defined in octal.
4698         See the subsection entitled "Non-printing characters" above for further         See the subsection entitled "Non-printing characters" above for further
4699         details of the handling of digits following a backslash.  There  is  no         details  of  the  handling of digits following a backslash. There is no
4700         such  problem  when named parentheses are used. A back reference to any         such problem when named parentheses are used. A back reference  to  any
4701         subpattern is possible using named parentheses (see below).         subpattern is possible using named parentheses (see below).
4702    
4703         Another way of avoiding the ambiguity inherent in  the  use  of  digits         Another  way  of  avoiding  the ambiguity inherent in the use of digits
4704         following  a  backslash  is  to use the \g escape sequence. This escape         following a backslash is to use the \g  escape  sequence.  This  escape
4705         must be followed by an unsigned number or a negative number, optionally         must be followed by an unsigned number or a negative number, optionally
4706         enclosed in braces. These examples are all identical:         enclosed in braces. These examples are all identical:
4707    
# Line 4671  BACK REFERENCES Line 4709  BACK REFERENCES
4709           (ring), \g1           (ring), \g1
4710           (ring), \g{1}           (ring), \g{1}
4711    
4712         An  unsigned number specifies an absolute reference without the ambigu-         An unsigned number specifies an absolute reference without the  ambigu-
4713         ity that is present in the older syntax. It is also useful when literal         ity that is present in the older syntax. It is also useful when literal
4714         digits follow the reference. A negative number is a relative reference.         digits follow the reference. A negative number is a relative reference.
4715         Consider this example:         Consider this example:
# Line 4679  BACK REFERENCES Line 4717  BACK REFERENCES
4717           (abc(def)ghi)\g{-1}           (abc(def)ghi)\g{-1}
4718    
4719         The sequence \g{-1} is a reference to the most recently started captur-         The sequence \g{-1} is a reference to the most recently started captur-
4720         ing  subpattern  before \g, that is, is it equivalent to \2. Similarly,         ing subpattern before \g, that is, is it equivalent to \2 in this exam-
4721         \g{-2} would be equivalent to \1. The use of relative references can be         ple.   Similarly, \g{-2} would be equivalent to \1. The use of relative
4722         helpful  in  long  patterns,  and  also in patterns that are created by         references can be helpful in long patterns, and also in  patterns  that
4723         joining together fragments that contain references within themselves.         are  created  by  joining  together  fragments  that contain references
4724           within themselves.
4725    
4726         A back reference matches whatever actually matched the  capturing  sub-         A back reference matches whatever actually matched the  capturing  sub-
4727         pattern  in  the  current subject string, rather than anything matching         pattern  in  the  current subject string, rather than anything matching
# Line 4802  ASSERTIONS Line 4841  ASSERTIONS
4841         most  convenient  way  to  do  it  is with (?!) because an empty string         most  convenient  way  to  do  it  is with (?!) because an empty string
4842         always matches, so an assertion that requires there not to be an  empty         always matches, so an assertion that requires there not to be an  empty
4843         string must always fail.  The backtracking control verb (*FAIL) or (*F)         string must always fail.  The backtracking control verb (*FAIL) or (*F)
4844         is essentially a synonym for (?!).         is a synonym for (?!).
4845    
4846     Lookbehind assertions     Lookbehind assertions
4847    
# Line 4945  CONDITIONAL SUBPATTERNS Line 4984  CONDITIONAL SUBPATTERNS
4984         the condition is true if a capturing subpattern of that number has pre-         the condition is true if a capturing subpattern of that number has pre-
4985         viously matched. If there is more than one  capturing  subpattern  with         viously matched. If there is more than one  capturing  subpattern  with
4986         the  same  number  (see  the earlier section about duplicate subpattern         the  same  number  (see  the earlier section about duplicate subpattern
4987         numbers), the condition is true if any of them have been set. An alter-         numbers), the condition is true if any of them have matched. An  alter-
4988         native  notation is to precede the digits with a plus or minus sign. In         native  notation is to precede the digits with a plus or minus sign. In
4989         this case, the subpattern number is relative rather than absolute.  The         this case, the subpattern number is relative rather than absolute.  The
4990         most  recently opened parentheses can be referenced by (?(-1), the next         most  recently opened parentheses can be referenced by (?(-1), the next
4991         most recent by (?(-2), and so on. In looping  constructs  it  can  also         most recent by (?(-2), and so on. Inside loops it can also  make  sense
4992         make  sense  to  refer  to  subsequent  groups  with constructs such as         to refer to subsequent groups. The next parentheses to be opened can be
4993         (?(+2).         referenced as (?(+1), and so on. (The value zero in any of these  forms
4994           is not used; it provokes a compile-time error.)
4995    
4996         Consider the following pattern, which  contains  non-significant  white         Consider  the  following  pattern, which contains non-significant white
4997         space to make it more readable (assume the PCRE_EXTENDED option) and to         space to make it more readable (assume the PCRE_EXTENDED option) and to
4998         divide it into three parts for ease of discussion:         divide it into three parts for ease of discussion:
4999    
5000           ( \( )?    [^()]+    (?(1) \) )           ( \( )?    [^()]+    (?(1) \) )
5001    
5002         The first part matches an optional opening  parenthesis,  and  if  that         The  first  part  matches  an optional opening parenthesis, and if that
5003         character is present, sets it as the first captured substring. The sec-         character is present, sets it as the first captured substring. The sec-
5004         ond part matches one or more characters that are not  parentheses.  The         ond  part  matches one or more characters that are not parentheses. The
5005         third part is a conditional subpattern that tests whether the first set         third part is a conditional subpattern that tests whether  or  not  the
5006         of parentheses matched or not. If they did, that is, if subject started         first  set  of  parentheses  matched.  If they did, that is, if subject
5007         with an opening parenthesis, the condition is true, and so the yes-pat-         started with an opening parenthesis, the condition is true, and so  the
5008         tern is executed and a  closing  parenthesis  is  required.  Otherwise,         yes-pattern  is  executed and a closing parenthesis is required. Other-
5009         since  no-pattern  is  not  present, the subpattern matches nothing. In         wise, since no-pattern is not present, the subpattern matches  nothing.
5010         other words,  this  pattern  matches  a  sequence  of  non-parentheses,         In  other  words,  this  pattern matches a sequence of non-parentheses,
5011         optionally enclosed in parentheses.         optionally enclosed in parentheses.
5012    
5013         If  you  were  embedding  this pattern in a larger one, you could use a         If you were embedding this pattern in a larger one,  you  could  use  a
5014         relative reference:         relative reference:
5015    
5016           ...other stuff... ( \( )?    [^()]+    (?(-1) \) ) ...           ...other stuff... ( \( )?    [^()]+    (?(-1) \) ) ...
5017    
5018         This makes the fragment independent of the parentheses  in  the  larger         This  makes  the  fragment independent of the parentheses in the larger
5019         pattern.         pattern.
5020    
5021     Checking for a used subpattern by name     Checking for a used subpattern by name
5022    
5023         Perl  uses  the  syntax  (?(<name>)...) or (?('name')...) to test for a         Perl uses the syntax (?(<name>)...) or (?('name')...)  to  test  for  a
5024         used subpattern by name. For compatibility  with  earlier  versions  of         used  subpattern  by  name.  For compatibility with earlier versions of
5025         PCRE,  which  had this facility before Perl, the syntax (?(name)...) is         PCRE, which had this facility before Perl, the syntax  (?(name)...)  is
5026         also recognized. However, there is a possible ambiguity with this  syn-         also  recognized. However, there is a possible ambiguity with this syn-
5027         tax,  because  subpattern  names  may  consist entirely of digits. PCRE         tax, because subpattern names may  consist  entirely  of  digits.  PCRE
5028         looks first for a named subpattern; if it cannot find one and the  name         looks  first for a named subpattern; if it cannot find one and the name
5029         consists  entirely  of digits, PCRE looks for a subpattern of that num-         consists entirely of digits, PCRE looks for a subpattern of  that  num-
5030         ber, which must be greater than zero. Using subpattern names that  con-         ber,  which must be greater than zero. Using subpattern names that con-
5031         sist entirely of digits is not recommended.         sist entirely of digits is not recommended.
5032    
5033         Rewriting the above example to use a named subpattern gives this:         Rewriting the above example to use a named subpattern gives this:
5034    
5035           (?<OPEN> \( )?    [^()]+    (?(<OPEN>) \) )           (?<OPEN> \( )?    [^()]+    (?(<OPEN>) \) )
5036    
5037         If  the  name used in a condition of this kind is a duplicate, the test         If the name used in a condition of this kind is a duplicate,  the  test
5038         is applied to all subpatterns of the same name, and is true if any  one         is  applied to all subpatterns of the same name, and is true if any one
5039         of them has matched.         of them has matched.
5040    
5041     Checking for pattern recursion     Checking for pattern recursion
5042    
5043         If the condition is the string (R), and there is no subpattern with the         If the condition is the string (R), and there is no subpattern with the
5044         name R, the condition is true if a recursive call to the whole  pattern         name  R, the condition is true if a recursive call to the whole pattern
5045         or any subpattern has been made. If digits or a name preceded by amper-         or any subpattern has been made. If digits or a name preceded by amper-
5046         sand follow the letter R, for example:         sand follow the letter R, for example:
5047    
# Line 5009  CONDITIONAL SUBPATTERNS Line 5049  CONDITIONAL SUBPATTERNS
5049    
5050         the condition is true if the most recent recursion is into a subpattern         the condition is true if the most recent recursion is into a subpattern
5051         whose number or name is given. This condition does not check the entire         whose number or name is given. This condition does not check the entire
5052         recursion stack. If the name used in a condition  of  this  kind  is  a         recursion  stack.  If  the  name  used in a condition of this kind is a
5053         duplicate, the test is applied to all subpatterns of the same name, and         duplicate, the test is applied to all subpatterns of the same name, and
5054         is true if any one of them is the most recent recursion.         is true if any one of them is the most recent recursion.
5055    
5056         At "top level", all these recursion test  conditions  are  false.   The         At  "top  level",  all  these recursion test conditions are false.  The
5057         syntax for recursive patterns is described below.         syntax for recursive patterns is described below.
5058    
5059     Defining subpatterns for use by reference only     Defining subpatterns for use by reference only
5060    
5061         If  the  condition  is  the string (DEFINE), and there is no subpattern         If the condition is the string (DEFINE), and  there  is  no  subpattern
5062         with the name DEFINE, the condition is  always  false.  In  this  case,         with  the  name  DEFINE,  the  condition is always false. In this case,
5063         there  may  be  only  one  alternative  in the subpattern. It is always         there may be only one alternative  in  the  subpattern.  It  is  always
5064         skipped if control reaches this point  in  the  pattern;  the  idea  of         skipped  if  control  reaches  this  point  in the pattern; the idea of
5065         DEFINE  is that it can be used to define "subroutines" that can be ref-         DEFINE is that it can be used to define "subroutines" that can be  ref-
5066         erenced from elsewhere. (The use of "subroutines" is described  below.)         erenced  from elsewhere. (The use of "subroutines" is described below.)
5067         For  example,  a pattern to match an IPv4 address could be written like         For  example,  a  pattern  to   match   an   IPv4   address   such   as
5068         this (ignore whitespace and line breaks):         "192.168.23.245" could be written like this (ignore whitespace and line
5069           breaks):
5070    
5071           (?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) )           (?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) )
5072           \b (?&byte) (\.(?&byte)){3} \b           \b (?&byte) (\.(?&byte)){3} \b
# Line 5242  RECURSIVE PATTERNS Line 5283  RECURSIVE PATTERNS
5283         remaining alternative is at a deeper recursion level, which PCRE cannot         remaining alternative is at a deeper recursion level, which PCRE cannot
5284         use.         use.
5285    
5286         To change the pattern so that matches all palindromic strings, not just         To  change  the pattern so that it matches all palindromic strings, not
5287         those with an odd number of characters, it is tempting  to  change  the         just those with an odd number of characters, it is tempting  to  change
5288         pattern to this:         the pattern to this:
5289    
5290           ^((.)(?1)\2|.?)$           ^((.)(?1)\2|.?)$
5291    
# Line 5411  BACKTRACKING CONTROL Line 5452  BACKTRACKING CONTROL
5452         character must be present. When one of these  optimizations  suppresses         character must be present. When one of these  optimizations  suppresses
5453         the  running  of  a match, any included backtracking verbs will not, of         the  running  of  a match, any included backtracking verbs will not, of
5454         course, be processed. You can suppress the start-of-match optimizations         course, be processed. You can suppress the start-of-match optimizations
5455         by setting the PCRE_NO_START_OPTIMIZE option when calling pcre_exec().         by  setting  the  PCRE_NO_START_OPTIMIZE  option when calling pcre_com-
5456           pile() or pcre_exec(), or by starting the pattern with (*NO_START_OPT).
5457    
5458     Verbs that act immediately     Verbs that act immediately
5459    
5460         The  following  verbs act as soon as they are encountered. They may not         The following verbs act as soon as they are encountered. They  may  not
5461         be followed by a name.         be followed by a name.
5462    
5463            (*ACCEPT)            (*ACCEPT)
5464    
5465         This verb causes the match to end successfully, skipping the  remainder         This  verb causes the match to end successfully, skipping the remainder
5466         of  the pattern. When inside a recursion, only the innermost pattern is         of the pattern. When inside a recursion, only the innermost pattern  is
5467         ended immediately. If (*ACCEPT) is inside  capturing  parentheses,  the         ended  immediately.  If  (*ACCEPT) is inside capturing parentheses, the
5468         data  so  far  is  captured. (This feature was added to PCRE at release         data so far is captured. (This feature was added  to  PCRE  at  release
5469         8.00.) For example:         8.00.) For example:
5470    
5471           A((?:A|B(*ACCEPT)|C)D)           A((?:A|B(*ACCEPT)|C)D)
5472    
5473         This matches "AB", "AAD", or "ACD"; when it matches "AB", "B"  is  cap-         This  matches  "AB", "AAD", or "ACD"; when it matches "AB", "B" is cap-
5474         tured by the outer parentheses.         tured by the outer parentheses.
5475    
5476           (*FAIL) or (*F)           (*FAIL) or (*F)
5477    
5478         This  verb  causes the match to fail, forcing backtracking to occur. It         This verb causes the match to fail, forcing backtracking to  occur.  It
5479         is equivalent to (?!) but easier to read. The Perl documentation  notes         is  equivalent to (?!) but easier to read. The Perl documentation notes
5480         that  it  is  probably  useful only when combined with (?{}) or (??{}).         that it is probably useful only when combined  with  (?{})  or  (??{}).
5481         Those are, of course, Perl features that are not present in  PCRE.  The         Those  are,  of course, Perl features that are not present in PCRE. The
5482         nearest  equivalent is the callout feature, as for example in this pat-         nearest equivalent is the callout feature, as for example in this  pat-
5483         tern:         tern:
5484    
5485           a+(?C)(*FAIL)           a+(?C)(*FAIL)
5486    
5487         A match with the string "aaaa" always fails, but the callout  is  taken         A  match  with the string "aaaa" always fails, but the callout is taken
5488         before each backtrack happens (in this example, 10 times).         before each backtrack happens (in this example, 10 times).
5489    
5490     Recording which path was taken     Recording which path was taken
5491    
5492         There  is  one  verb  whose  main  purpose  is to track how a match was         There is one verb whose main purpose  is  to  track  how  a  match  was
5493         arrived at, though it also has a  secondary  use  in  conjunction  with         arrived  at,  though  it  also  has a secondary use in conjunction with
5494         advancing the match starting point (see (*SKIP) below).         advancing the match starting point (see (*SKIP) below).
5495    
5496           (*MARK:NAME) or (*:NAME)           (*MARK:NAME) or (*:NAME)
5497    
5498         A  name  is  always  required  with  this  verb.  There  may be as many         A name is always  required  with  this  verb.  There  may  be  as  many
5499         instances of (*MARK) as you like in a pattern, and their names  do  not         instances  of  (*MARK) as you like in a pattern, and their names do not
5500         have to be unique.         have to be unique.
5501    
5502         When  a  match  succeeds,  the  name of the last-encountered (*MARK) is         When a match succeeds, the name  of  the  last-encountered  (*MARK)  is
5503         passed back to  the  caller  via  the  pcre_extra  data  structure,  as         passed  back  to  the  caller  via  the  pcre_extra  data structure, as
5504         described in the section on pcre_extra in the pcreapi documentation. No         described in the section on pcre_extra in the pcreapi documentation. No
5505         data is returned for a partial match. Here is an  example  of  pcretest         data  is  returned  for a partial match. Here is an example of pcretest
5506         output,  where the /K modifier requests the retrieval and outputting of         output, where the /K modifier requests the retrieval and outputting  of
5507         (*MARK) data:         (*MARK) data:
5508    
5509           /X(*MARK:A)Y|X(*MARK:B)Z/K           /X(*MARK:A)Y|X(*MARK:B)Z/K
# Line 5473  BACKTRACKING CONTROL Line 5515  BACKTRACKING CONTROL
5515           MK: B           MK: B
5516    
5517         The (*MARK) name is tagged with "MK:" in this output, and in this exam-         The (*MARK) name is tagged with "MK:" in this output, and in this exam-
5518         ple  it indicates which of the two alternatives matched. This is a more         ple it indicates which of the two alternatives matched. This is a  more
5519         efficient way of obtaining this information than putting each  alterna-         efficient  way of obtaining this information than putting each alterna-
5520         tive in its own capturing parentheses.         tive in its own capturing parentheses.
5521    
5522         A  name  may  also  be  returned after a failed match if the final path         A name may also be returned after a failed  match  if  the  final  path
5523         through the pattern involves (*MARK). However, unless (*MARK)  used  in         through  the  pattern involves (*MARK). However, unless (*MARK) used in
5524         conjunction  with  (*COMMIT),  this  is unlikely to happen for an unan-         conjunction with (*COMMIT), this is unlikely to  happen  for  an  unan-
5525         chored pattern because, as the starting point for matching is advanced,         chored pattern because, as the starting point for matching is advanced,
5526         the final check is often with an empty string, causing a failure before         the final check is often with an empty string, causing a failure before
5527         (*MARK) is reached. For example:         (*MARK) is reached. For example:
# Line 5489  BACKTRACKING CONTROL Line 5531  BACKTRACKING CONTROL
5531           No match           No match
5532    
5533         There are three potential starting points for this match (starting with         There are three potential starting points for this match (starting with
5534         X,  starting  with  P,  and  with  an  empty string). If the pattern is         X, starting with P, and with  an  empty  string).  If  the  pattern  is
5535         anchored, the result is different:         anchored, the result is different:
5536    
5537           /^X(*MARK:A)Y|^X(*MARK:B)Z/K           /^X(*MARK:A)Y|^X(*MARK:B)Z/K
5538           XP           XP
5539           No match, mark = B           No match, mark = B
5540    
5541         PCRE's start-of-match optimizations can also interfere with  this.  For         PCRE's  start-of-match  optimizations can also interfere with this. For
5542         example,  if, as a result of a call to pcre_study(), it knows the mini-         example, if, as a result of a call to pcre_study(), it knows the  mini-
5543         mum subject length for a match, a shorter subject will not  be  scanned         mum  subject  length for a match, a shorter subject will not be scanned
5544         at all.         at all.
5545    
5546         Note that similar anomalies (though different in detail) exist in Perl,         Note that similar anomalies (though different in detail) exist in Perl,
5547         no doubt for the same reasons. The use of (*MARK) data after  a  failed         no  doubt  for the same reasons. The use of (*MARK) data after a failed
5548         match  of an unanchored pattern is not recommended, unless (*COMMIT) is         match of an unanchored pattern is not recommended, unless (*COMMIT)  is
5549         involved.         involved.
5550    
5551     Verbs that act after backtracking     Verbs that act after backtracking
5552    
5553         The following verbs do nothing when they are encountered. Matching con-         The following verbs do nothing when they are encountered. Matching con-
5554         tinues  with what follows, but if there is no subsequent match, causing         tinues with what follows, but if there is no subsequent match,  causing
5555         a backtrack to the verb, a failure is  forced.  That  is,  backtracking         a  backtrack  to  the  verb, a failure is forced. That is, backtracking
5556         cannot  pass  to the left of the verb. However, when one of these verbs         cannot pass to the left of the verb. However, when one of  these  verbs
5557         appears inside an atomic group, its effect is confined to  that  group,         appears  inside  an atomic group, its effect is confined to that group,
5558         because  once the group has been matched, there is never any backtrack-         because once the group has been matched, there is never any  backtrack-
5559         ing into it. In this situation, backtracking can  "jump  back"  to  the         ing  into  it.  In  this situation, backtracking can "jump back" to the
5560         left  of the entire atomic group. (Remember also, as stated above, that         left of the entire atomic group. (Remember also, as stated above,  that
5561         this localization also applies in subroutine calls and assertions.)         this localization also applies in subroutine calls and assertions.)
5562    
5563         These verbs differ in exactly what kind of failure  occurs  when  back-         These  verbs  differ  in exactly what kind of failure occurs when back-
5564         tracking reaches them.         tracking reaches them.
5565    
5566           (*COMMIT)           (*COMMIT)
5567    
5568         This  verb, which may not be followed by a name, causes the whole match         This verb, which may not be followed by a name, causes the whole  match
5569         to fail outright if the rest of the pattern does not match. Even if the         to fail outright if the rest of the pattern does not match. Even if the
5570         pattern is unanchored, no further attempts to find a match by advancing         pattern is unanchored, no further attempts to find a match by advancing
5571         the  starting  point  take  place.  Once  (*COMMIT)  has  been  passed,         the  starting  point  take  place.  Once  (*COMMIT)  has  been  passed,
5572         pcre_exec()  is  committed  to  finding a match at the current starting         pcre_exec() is committed to finding a match  at  the  current  starting
5573         point, or not at all. For example:         point, or not at all. For example:
5574    
5575           a+(*COMMIT)b           a+(*COMMIT)b
5576    
5577         This matches "xxaab" but not "aacaab". It can be thought of as  a  kind         This  matches  "xxaab" but not "aacaab". It can be thought of as a kind
5578         of dynamic anchor, or "I've started, so I must finish." The name of the         of dynamic anchor, or "I've started, so I must finish." The name of the
5579         most recently passed (*MARK) in the path is passed back when  (*COMMIT)         most  recently passed (*MARK) in the path is passed back when (*COMMIT)
5580         forces a match failure.         forces a match failure.
5581    
5582         Note  that  (*COMMIT)  at  the start of a pattern is not the same as an         Note that (*COMMIT) at the start of a pattern is not  the  same  as  an
5583         anchor, unless PCRE's start-of-match optimizations are turned  off,  as         anchor,  unless  PCRE's start-of-match optimizations are turned off, as
5584         shown in this pcretest example:         shown in this pcretest example:
5585    
5586           /(*COMMIT)abc/           /(*COMMIT)abc/
# Line 5547  BACKTRACKING CONTROL Line 5589  BACKTRACKING CONTROL
5589           xyzabc\Y           xyzabc\Y
5590           No match           No match
5591    
5592         PCRE  knows  that  any  match  must start with "a", so the optimization         PCRE knows that any match must start  with  "a",  so  the  optimization
5593         skips along the subject to "a" before running the first match  attempt,         skips  along the subject to "a" before running the first match attempt,
5594         which  succeeds.  When the optimization is disabled by the \Y escape in         which succeeds. When the optimization is disabled by the \Y  escape  in
5595         the second subject, the match starts at "x" and so the (*COMMIT) causes         the second subject, the match starts at "x" and so the (*COMMIT) causes
5596         it to fail without trying any other starting points.         it to fail without trying any other starting points.
5597    
5598           (*PRUNE) or (*PRUNE:NAME)           (*PRUNE) or (*PRUNE:NAME)
5599    
5600         This  verb causes the match to fail at the current starting position in         This verb causes the match to fail at the current starting position  in
5601         the subject if the rest of the pattern does not match. If  the  pattern         the  subject  if the rest of the pattern does not match. If the pattern
5602         is  unanchored,  the  normal  "bumpalong"  advance to the next starting         is unanchored, the normal "bumpalong"  advance  to  the  next  starting
5603         character then happens. Backtracking can occur as usual to the left  of         character  then happens. Backtracking can occur as usual to the left of
5604         (*PRUNE),  before  it  is  reached,  or  when  matching to the right of         (*PRUNE), before it is reached,  or  when  matching  to  the  right  of
5605         (*PRUNE), but if there is no match to the  right,  backtracking  cannot         (*PRUNE),  but  if  there is no match to the right, backtracking cannot
5606         cross  (*PRUNE). In simple cases, the use of (*PRUNE) is just an alter-         cross (*PRUNE). In simple cases, the use of (*PRUNE) is just an  alter-
5607         native to an atomic group or possessive quantifier, but there are  some         native  to an atomic group or possessive quantifier, but there are some
5608         uses of (*PRUNE) that cannot be expressed in any other way.  The behav-         uses of (*PRUNE) that cannot be expressed in any other way.  The behav-
5609         iour of (*PRUNE:NAME) is the  same  as  (*MARK:NAME)(*PRUNE)  when  the         iour  of  (*PRUNE:NAME)  is  the  same as (*MARK:NAME)(*PRUNE) when the
5610         match  fails  completely;  the name is passed back if this is the final         match fails completely; the name is passed back if this  is  the  final
5611         attempt.  (*PRUNE:NAME) does not pass back a name  if  the  match  suc-         attempt.   (*PRUNE:NAME)  does  not  pass back a name if the match suc-
5612         ceeds.  In  an  anchored pattern (*PRUNE) has the same effect as (*COM-         ceeds. In an anchored pattern (*PRUNE) has the same  effect  as  (*COM-
5613         MIT).         MIT).
5614    
5615           (*SKIP)           (*SKIP)
5616    
5617         This verb, when given without a name, is like (*PRUNE), except that  if         This  verb, when given without a name, is like (*PRUNE), except that if
5618         the  pattern  is unanchored, the "bumpalong" advance is not to the next         the pattern is unanchored, the "bumpalong" advance is not to  the  next
5619         character, but to the position in the subject where (*SKIP) was encoun-         character, but to the position in the subject where (*SKIP) was encoun-
5620         tered.  (*SKIP)  signifies that whatever text was matched leading up to         tered. (*SKIP) signifies that whatever text was matched leading  up  to
5621         it cannot be part of a successful match. Consider:         it cannot be part of a successful match. Consider:
5622    
5623           a+(*SKIP)b           a+(*SKIP)b
5624    
5625         If the subject is "aaaac...",  after  the  first  match  attempt  fails         If  the  subject  is  "aaaac...",  after  the first match attempt fails
5626         (starting  at  the  first  character in the string), the starting point         (starting at the first character in the  string),  the  starting  point
5627         skips on to start the next attempt at "c". Note that a possessive quan-         skips on to start the next attempt at "c". Note that a possessive quan-
5628         tifer  does not have the same effect as this example; although it would         tifer does not have the same effect as this example; although it  would
5629         suppress backtracking  during  the  first  match  attempt,  the  second         suppress  backtracking  during  the  first  match  attempt,  the second
5630         attempt  would  start at the second character instead of skipping on to         attempt would start at the second character instead of skipping  on  to
5631         "c".         "c".
5632    
5633           (*SKIP:NAME)           (*SKIP:NAME)
5634    
5635         When (*SKIP) has an associated name, its behaviour is modified. If  the         When  (*SKIP) has an associated name, its behaviour is modified. If the
5636         following pattern fails to match, the previous path through the pattern         following pattern fails to match, the previous path through the pattern
5637         is searched for the most recent (*MARK) that has the same name. If  one         is  searched for the most recent (*MARK) that has the same name. If one
5638         is  found, the "bumpalong" advance is to the subject position that cor-         is found, the "bumpalong" advance is to the subject position that  cor-
5639         responds to that (*MARK) instead of to where (*SKIP)  was  encountered.         responds  to  that (*MARK) instead of to where (*SKIP) was encountered.
5640         If  no (*MARK) with a matching name is found, normal "bumpalong" of one         If no (*MARK) with a matching name is found, normal "bumpalong" of  one
5641         character happens (the (*SKIP) is ignored).         character happens (the (*SKIP) is ignored).
5642    
5643           (*THEN) or (*THEN:NAME)           (*THEN) or (*THEN:NAME)
5644    
5645         This verb causes a skip  to  the  next  alternation  in  the  innermost         This  verb  causes  a  skip  to  the  next alternation in the innermost
5646         enclosing  group if the rest of the pattern does not match. That is, it         enclosing group if the rest of the pattern does not match. That is,  it
5647         cancels pending backtracking, but only within the current  alternation.         cancels  pending backtracking, but only within the current alternation.
5648         Its  name comes from the observation that it can be used for a pattern-         Its name comes from the observation that it can be used for a  pattern-
5649         based if-then-else block:         based if-then-else block:
5650    
5651           ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ...           ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ...
5652    
5653         If the COND1 pattern matches, FOO is tried (and possibly further  items         If  the COND1 pattern matches, FOO is tried (and possibly further items
5654         after  the  end  of  the group if FOO succeeds); on failure the matcher         after the end of the group if FOO succeeds);  on  failure  the  matcher
5655         skips to the second alternative and tries COND2,  without  backtracking         skips  to  the second alternative and tries COND2, without backtracking
5656         into  COND1.  The  behaviour  of  (*THEN:NAME)  is  exactly the same as         into COND1. The behaviour  of  (*THEN:NAME)  is  exactly  the  same  as
5657         (*MARK:NAME)(*THEN) if the overall  match  fails.  If  (*THEN)  is  not         (*MARK:NAME)(*THEN)  if  the  overall  match  fails.  If (*THEN) is not
5658         directly inside an alternation, it acts like (*PRUNE).         directly inside an alternation, it acts like (*PRUNE).
5659    
5660         The above verbs provide four different "strengths" of control when sub-         The above verbs provide four different "strengths" of control when sub-
5661         sequent matching fails. (*THEN) is the weakest, carrying on  the  match         sequent  matching  fails. (*THEN) is the weakest, carrying on the match
5662         at  the next alternation. (*PRUNE) comes next, failing the match at the         at the next alternation. (*PRUNE) comes next, failing the match at  the
5663         current starting position, but allowing an advance to the next  charac-         current  starting position, but allowing an advance to the next charac-
5664         ter  (for  an  unanchored pattern). (*SKIP) is similar, except that the         ter (for an unanchored pattern). (*SKIP) is similar,  except  that  the
5665         advance may be more than one character.  (*COMMIT)  is  the  strongest,         advance  may  be  more  than one character. (*COMMIT) is the strongest,
5666         causing the entire match to fail.         causing the entire match to fail.
5667    
5668         If  more than one is present in a pattern, the "stongest" one wins. For         If more than one is present in a pattern, the "stongest" one wins.  For
5669         example, consider this pattern, where A, B, etc.  are  complex  pattern         example,  consider  this  pattern, where A, B, etc. are complex pattern
5670         fragments:         fragments:
5671    
5672           (A(*COMMIT)B(*THEN)C|D)           (A(*COMMIT)B(*THEN)C|D)
5673    
5674         Once  A  has  matched,  PCRE is committed to this match, at the current         Once A has matched, PCRE is committed to this  match,  at  the  current
5675         starting position. If subsequently B matches, but C does not, the  nor-         starting  position. If subsequently B matches, but C does not, the nor-
5676         mal (*THEN) action of trying the next alternation (that is, D) does not         mal (*THEN) action of trying the next alternation (that is, D) does not
5677         happen because (*COMMIT) overrides.         happen because (*COMMIT) overrides.
5678    
# Line 5649  AUTHOR Line 5691  AUTHOR
5691    
5692  REVISION  REVISION
5693    
5694         Last updated: 17 November 2010         Last updated: 21 November 2010
5695         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
5696  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
5697    
5698    
5699  PCRESYNTAX(3)                                                    PCRESYNTAX(3)  PCRESYNTAX(3)                                                    PCRESYNTAX(3)
5700    
5701    
# Line 5677  QUOTING Line 5719  QUOTING
5719  CHARACTERS  CHARACTERS
5720    
5721           \a         alarm, that is, the BEL character (hex 07)           \a         alarm, that is, the BEL character (hex 07)
5722           \cx        "control-x", where x is any character           \cx        "control-x", where x is any ASCII character
5723           \e         escape (hex 1B)           \e         escape (hex 1B)
5724           \f         formfeed (hex 0C)           \f         formfeed (hex 0C)
5725           \n         newline (hex 0A)           \n         newline (hex 0A)
# Line 5896  OPTION SETTING Line 5938  OPTION SETTING
5938         The following are recognized only at the start of a  pattern  or  after         The following are recognized only at the start of a  pattern  or  after
5939         one of the newline-setting options with similar syntax:         one of the newline-setting options with similar syntax:
5940    
5941             (*NO_START_OPT) no start-match optimization (PCRE_NO_START_OPTIMIZE)
5942           (*UTF8)         set UTF-8 mode (PCRE_UTF8)           (*UTF8)         set UTF-8 mode (PCRE_UTF8)
5943           (*UCP)          set PCRE_UCP (use Unicode properties for \d etc)           (*UCP)          set PCRE_UCP (use Unicode properties for \d etc)
5944    
# Line 6018  AUTHOR Line 6061  AUTHOR
6061    
6062  REVISION  REVISION
6063    
6064         Last updated: 12 May 2010         Last updated: 21 November 2010
6065         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
6066  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
6067    
6068    
6069  PCREPARTIAL(3)                                                  PCREPARTIAL(3)  PCREPARTIAL(3)                                                  PCREPARTIAL(3)
6070    
6071    
# Line 6441  REVISION Line 6484  REVISION
6484         Last updated: 07 November 2010         Last updated: 07 November 2010
6485         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
6486  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
6487    
6488    
6489  PCREPRECOMPILE(3)                                            PCREPRECOMPILE(3)  PCREPRECOMPILE(3)                                            PCREPRECOMPILE(3)
6490    
6491    
# Line 6550  COMPATIBILITY WITH DIFFERENT PCRE RELEAS Line 6593  COMPATIBILITY WITH DIFFERENT PCRE RELEAS
6593    
6594         In general, it is safest to  recompile  all  saved  patterns  when  you         In general, it is safest to  recompile  all  saved  patterns  when  you
6595         update  to  a new PCRE release, though not all updates actually require         update  to  a new PCRE release, though not all updates actually require
6596         this. Recompiling is definitely needed for release 7.2.         this.
6597    
6598    
6599  AUTHOR  AUTHOR
# Line 6562  AUTHOR Line 6605  AUTHOR
6605    
6606  REVISION  REVISION
6607    
6608         Last updated: 13 June 2007         Last updated: 17 November 2010
6609         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
6610  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
6611    
6612    
6613  PCREPERFORM(3)                                                  PCREPERFORM(3)  PCREPERFORM(3)                                                  PCREPERFORM(3)
6614    
6615    
# Line 6733  REVISION Line 6776  REVISION
6776         Last updated: 16 May 2010         Last updated: 16 May 2010
6777         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
6778  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
6779    
6780    
6781  PCREPOSIX(3)             &nb