/[pcre]/code/trunk/doc/pcre.txt
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revision 511 by ph10, Wed Mar 10 16:08:01 2010 UTC revision 512 by ph10, Tue Mar 30 11:11:52 2010 UTC
# Line 1469  COMPILATION ERROR CODES Line 1469  COMPILATION ERROR CODES
1469           57  \g is not followed by a braced, angle-bracketed, or quoted           57  \g is not followed by a braced, angle-bracketed, or quoted
1470                 name/number or by a plain number                 name/number or by a plain number
1471           58  a numbered reference must not be zero           58  a numbered reference must not be zero
1472           59  (*VERB) with an argument is not supported           59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1473           60  (*VERB) not recognized           60  (*VERB) not recognized
1474           61  number is too big           61  number is too big
1475           62  subpattern name expected           62  subpattern name expected
1476           63  digit expected after (?+           63  digit expected after (?+
1477           64  ] is an invalid data character in JavaScript compatibility mode           64  ] is an invalid data character in JavaScript compatibility mode
1478             65  different names for  subpatterns  of  the  same  number  are  not
1479           allowed
1480             66  (*MARK) must have an argument
1481    
1482         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
1483         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.
1484    
1485    
# Line 1485  STUDYING A PATTERN Line 1488  STUDYING A PATTERN
1488         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1489              const char **errptr);              const char **errptr);
1490    
1491         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
1492         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
1493         matching.  The function pcre_study() takes a pointer to a compiled pat-         matching. The function pcre_study() takes a pointer to a compiled  pat-
1494         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1495         information  that  will  help speed up matching, pcre_study() returns a         information that will help speed up matching,  pcre_study()  returns  a
1496         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
1497         the results of the study.         the results of the study.
1498    
1499         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1500         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-
1501         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
1502         passed; these are described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1503    
1504         If studying the  pattern  does  not  produce  any  useful  information,         If  studying  the  pattern  does  not  produce  any useful information,
1505         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1506         wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or         wants   to   pass   any   of   the   other  fields  to  pcre_exec()  or
1507         pcre_dfa_exec(), it must set up its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1508    
1509         The  second  argument of pcre_study() contains option bits. At present,         The second argument of pcre_study() contains option bits.  At  present,
1510         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1511    
1512         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.
1513         If  studying  succeeds  (even  if no data is returned), the variable it         If studying succeeds (even if no data is  returned),  the  variable  it
1514         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
1515         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
1516         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
1517         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1518    
1519         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1524  STUDYING A PATTERN Line 1527  STUDYING A PATTERN
1527         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
1528         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
1529         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
1530         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
1531         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
1532         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
1533         the value in a calling program via the pcre_fullinfo() function.         the value in a calling program via the pcre_fullinfo() function.
1534    
1535         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
1536         have a single fixed starting character. A bitmap of  possible  starting         have  a  single fixed starting character. A bitmap of possible starting
1537         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
1538         which to start matching.         which to start matching.
1539    
1540    
1541  LOCALE SUPPORT  LOCALE SUPPORT
1542    
1543         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1544         letters,  digits, or whatever, by reference to a set of tables, indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1545         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
1546         characters  with  codes  less than 128. Higher-valued codes never match         characters with codes less than 128. Higher-valued  codes  never  match
1547         escapes such as \w or \d, but can be tested with \p if  PCRE  is  built         escapes  such  as  \w or \d, but can be tested with \p if PCRE is built
1548         with  Unicode  character property support. The use of locales with Uni-         with Unicode character property support. The use of locales  with  Uni-
1549         code is discouraged. If you are handling characters with codes  greater         code  is discouraged. If you are handling characters with codes greater
1550         than  128, you should either use UTF-8 and Unicode, or use locales, but         than 128, you should either use UTF-8 and Unicode, or use locales,  but
1551         not try to mix the two.         not try to mix the two.
1552    
1553         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
1554         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1555         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1556         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-
1557         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,
1558         which may cause them to be different.         which may cause them to be different.
1559    
1560         The  internal tables can always be overridden by tables supplied by the         The internal tables can always be overridden by tables supplied by  the
1561         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1562         from  the  default.  As more and more applications change to using Uni-         from the default. As more and more applications change  to  using  Uni-
1563         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
1564    
1565         External tables are built by calling  the  pcre_maketables()  function,         External  tables  are  built by calling the pcre_maketables() function,
1566         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
1567         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1568         example,  to  build  and use tables that are appropriate for the French         example, to build and use tables that are appropriate  for  the  French
1569         locale (where accented characters with  values  greater  than  128  are         locale  (where  accented  characters  with  values greater than 128 are
1570         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1571    
1572           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1573           tables = pcre_maketables();           tables = pcre_maketables();
1574           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1575    
1576         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;
1577         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".
1578    
1579         When pcre_maketables() runs, the tables are built  in  memory  that  is         When  pcre_maketables()  runs,  the  tables are built in memory that is
1580         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1581         that the memory containing the tables remains available for as long  as         that  the memory containing the tables remains available for as long as
1582         it is needed.         it is needed.
1583    
1584         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
1585         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()
1586         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-
1587         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1588         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1589    
1590         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
1591         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1592         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
1593         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
1594         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1595    
# Line 1596  INFORMATION ABOUT A PATTERN Line 1599  INFORMATION ABOUT A PATTERN
1599         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1600              int what, void *where);              int what, void *where);
1601    
1602         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1603         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1604         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1605    
1606         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1607         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
1608         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1609         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
1610         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
1611         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1612    
1613           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1612  INFORMATION ABOUT A PATTERN Line 1615  INFORMATION ABOUT A PATTERN
1615           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1616           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1617    
1618         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
1619         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1620         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1621         pattern:         pattern:
1622    
1623           int rc;           int rc;
# Line 1625  INFORMATION ABOUT A PATTERN Line 1628  INFORMATION ABOUT A PATTERN
1628             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1629             &length);         /* where to put the data */             &length);         /* where to put the data */
1630    
1631         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
1632         are as follows:         are as follows:
1633    
1634           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1635    
1636         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1637         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1638         there are no back references.         there are no back references.
1639    
1640           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1641    
1642         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1643         argument should point to an int variable.         argument should point to an int variable.
1644    
1645           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1646    
1647         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1648         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1649         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1650         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1651         passing a NULL table pointer.         passing a NULL table pointer.
1652    
1653           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1654    
1655         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1656         non-anchored pattern. The fourth argument should point to an int  vari-         non-anchored  pattern. The fourth argument should point to an int vari-
1657         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
1658         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1659    
1660         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
1661         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1662    
1663         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1664         branch starts with "^", or         branch starts with "^", or
1665    
1666         (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
1667         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1668    
1669         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1670         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1671         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1672    
1673           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1674    
1675         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
1676         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
1677         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1678         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1679         able.         able.
1680    
1681           PCRE_INFO_HASCRORLF           PCRE_INFO_HASCRORLF
1682    
1683         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
1684         characters, otherwise 0. The fourth argument should  point  to  an  int         characters,  otherwise  0.  The  fourth argument should point to an int
1685         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
1686         \r or \n.         \r or \n.
1687    
1688           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1689    
1690         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,
1691         otherwise  0. The fourth argument should point to an int variable. (?J)         otherwise 0. The fourth argument should point to an int variable.  (?J)
1692         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1693    
1694           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1695    
1696         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
1697         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
1698         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1699         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
1700         byte is recorded only if it follows something of variable  length.  For         byte  is  recorded only if it follows something of variable length. For
1701         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
1702         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1703    
1704           PCRE_INFO_MINLENGTH           PCRE_INFO_MINLENGTH
1705    
1706         If the pattern was studied and a minimum length  for  matching  subject         If  the  pattern  was studied and a minimum length for matching subject
1707         strings  was  computed,  its  value is returned. Otherwise the returned         strings was computed, its value is  returned.  Otherwise  the  returned
1708         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
1709         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
1710         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
1711         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
1712         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.
1713    
1714           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1715           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1716           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1717    
1718         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE  supports the use of named as well as numbered capturing parenthe-
1719         ses.  The names are just an additional way of identifying the parenthe-         ses. The names are just an additional way of identifying the  parenthe-
1720         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
1721         pcre_get_named_substring()  are  provided  for extracting captured sub-         pcre_get_named_substring() are provided for  extracting  captured  sub-
1722         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
1723         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
1724         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
1725         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
1726         described by these three values.         described by these three values.
1727    
1728         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
1729         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1730         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
1731         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
1732         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
1733         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-
1734         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-
1735         sponding name, zero terminated.         sponding name, zero terminated.
1736    
1737         The  names are in alphabetical order. Duplicate names may appear if (?|         The names are in alphabetical order. Duplicate names may appear if  (?|
1738         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
1739         the  section  on  duplicate subpattern numbers in the pcrepattern page.         the section on duplicate subpattern numbers in  the  pcrepattern  page.
1740         Duplicate names for subpatterns with different  numbers  are  permitted         Duplicate  names  for  subpatterns with different numbers are permitted
1741         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
1742         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-
1743         tern.  In  the  absence  of (?| this is the order of increasing number;         tern. In the absence of (?| this is the  order  of  increasing  number;
1744         when (?| is used this is not necessarily the case because later subpat-         when (?| is used this is not necessarily the case because later subpat-
1745         terns may have lower numbers.         terns may have lower numbers.
1746    
1747         As  a  simple  example of the name/number table, consider the following         As a simple example of the name/number table,  consider  the  following
1748         pattern (assume PCRE_EXTENDED is set, so white space -  including  new-         pattern  (assume  PCRE_EXTENDED is set, so white space - including new-
1749         lines - is ignored):         lines - is ignored):
1750    
1751           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1752           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1753    
1754         There  are  four  named subpatterns, so the table has four entries, and         There are four named subpatterns, so the table has  four  entries,  and
1755         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,
1756         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1757         as ??:         as ??:
1758    
# Line 1758  INFORMATION ABOUT A PATTERN Line 1761  INFORMATION ABOUT A PATTERN
1761           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1762           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1763    
1764         When writing code to extract data  from  named  subpatterns  using  the         When  writing  code  to  extract  data from named subpatterns using the
1765         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
1766         to be different for each compiled pattern.         to be different for each compiled pattern.
1767    
1768           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1769    
1770         Return 1  if  the  pattern  can  be  used  for  partial  matching  with         Return  1  if  the  pattern  can  be  used  for  partial  matching with
1771         pcre_exec(),  otherwise  0.  The fourth argument should point to an int         pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1772         variable. From  release  8.00,  this  always  returns  1,  because  the         variable.  From  release  8.00,  this  always  returns  1,  because the
1773         restrictions  that  previously  applied  to  partial matching have been         restrictions that previously applied  to  partial  matching  have  been
1774         lifted. The pcrepartial documentation gives details of  partial  match-         lifted.  The  pcrepartial documentation gives details of partial match-
1775         ing.         ing.
1776    
1777           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1778    
1779         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
1780         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1781         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1782         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
1783         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
1784         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
1785         the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,         the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1786         and PCRE_EXTENDED.         and PCRE_EXTENDED.
1787    
1788         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
1789         alternatives begin with one of the following:         alternatives begin with one of the following:
1790    
1791           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1796  INFORMATION ABOUT A PATTERN Line 1799  INFORMATION ABOUT A PATTERN
1799    
1800           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1801    
1802         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
1803         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
1804         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
1805         size_t variable.         size_t variable.
# Line 1804  INFORMATION ABOUT A PATTERN Line 1807  INFORMATION ABOUT A PATTERN
1807           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1808    
1809         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
1810         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
1811         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
1812         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
1813         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
1814         variable.         variable.
1815    
1816    
# Line 1815  OBSOLETE INFO FUNCTION Line 1818  OBSOLETE INFO FUNCTION
1818    
1819         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1820    
1821         The pcre_info() function is now obsolete because its interface  is  too         The  pcre_info()  function is now obsolete because its interface is too
1822         restrictive  to return all the available data about a compiled pattern.         restrictive to return all the available data about a compiled  pattern.
1823         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
1824         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-
1825         lowing negative numbers:         lowing negative numbers:
1826    
1827           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1828           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1829    
1830         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
1831         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
1832         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1833    
1834         If the pattern is not anchored and the  firstcharptr  argument  is  not         If  the  pattern  is  not anchored and the firstcharptr argument is not
1835         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
1836         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1837    
1838    
# Line 1837  REFERENCE COUNTS Line 1840  REFERENCE COUNTS
1840    
1841         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1842    
1843         The pcre_refcount() function is used to maintain a reference  count  in         The  pcre_refcount()  function is used to maintain a reference count in
1844         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
1845         benefit of applications that  operate  in  an  object-oriented  manner,         benefit  of  applications  that  operate  in an object-oriented manner,
1846         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1847         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.
1848    
1849         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1850         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
1851         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
1852         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
1853         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
1854         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1855    
1856         Except  when it is zero, the reference count is not correctly preserved         Except when it is zero, the reference count is not correctly  preserved
1857         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
1858         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1859    
1860    
# Line 1861  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1864  MATCHING A PATTERN: THE TRADITIONAL FUNC
1864              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1865              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1866    
1867         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
1868         compiled pattern, which is passed in the code argument. If the  pattern         compiled  pattern, which is passed in the code argument. If the pattern
1869         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
1870         argument. This function is the main matching facility of  the  library,         argument.  This  function is the main matching facility of the library,
1871         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
1872         an alternative matching function, which is described below in the  sec-         an  alternative matching function, which is described below in the sec-
1873         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1874    
1875         In  most applications, the pattern will have been compiled (and option-         In most applications, the pattern will have been compiled (and  option-
1876         ally studied) in the same process that calls pcre_exec().  However,  it         ally  studied)  in the same process that calls pcre_exec(). However, it
1877         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
1878         later in different processes, possibly even on different hosts.  For  a         later  in  different processes, possibly even on different hosts. For a
1879         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1880    
1881         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1891  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1894  MATCHING A PATTERN: THE TRADITIONAL FUNC
1894    
1895     Extra data for pcre_exec()     Extra data for pcre_exec()
1896    
1897         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
1898         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
1899         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-
1900         tional information in it. The pcre_extra block contains  the  following         tional  information  in it. The pcre_extra block contains the following
1901         fields (not necessarily in this order):         fields (not necessarily in this order):
1902    
1903           unsigned long int flags;           unsigned long int flags;
# Line 1903  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1906  MATCHING A PATTERN: THE TRADITIONAL FUNC
1906           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
1907           void *callout_data;           void *callout_data;
1908           const unsigned char *tables;           const unsigned char *tables;
1909             unsigned char **mark;
1910    
1911         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
1912         are set. The flag bits are:         are set. The flag bits are:
1913    
1914           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1912  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1916  MATCHING A PATTERN: THE TRADITIONAL FUNC
1916           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
1917           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1918           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1919             PCRE_EXTRA_MARK
1920    
1921         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
1922         the  pcre_extra  block  that is returned by pcre_study(), together with         the pcre_extra block that is returned by  pcre_study(),  together  with
1923         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
1924         add  to  the  block by setting the other fields and their corresponding         add to the block by setting the other fields  and  their  corresponding
1925         flag bits.         flag bits.
1926    
1927         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
1928         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
1929         match, but which have a very large number  of  possibilities  in  their         match,  but  which  have  a very large number of possibilities in their
1930         search  trees. The classic example is a pattern that uses nested unlim-         search trees. The classic example is a pattern that uses nested  unlim-
1931         ited repeats.         ited repeats.
1932    
1933         Internally, PCRE uses a function called match() which it calls  repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1934         edly  (sometimes  recursively). The limit set by match_limit is imposed         edly (sometimes recursively). The limit set by match_limit  is  imposed
1935         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
1936         has  the  effect  of  limiting the amount of backtracking that can take         has the effect of limiting the amount of  backtracking  that  can  take
1937         place. For patterns that are not anchored, the count restarts from zero         place. For patterns that are not anchored, the count restarts from zero
1938         for each position in the subject string.         for each position in the subject string.
1939    
1940         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
1941         default default is 10 million, which handles all but the  most  extreme         default  default  is 10 million, which handles all but the most extreme
1942         cases.  You  can  override  the  default by suppling pcre_exec() with a         cases. You can override the default  by  suppling  pcre_exec()  with  a
1943         pcre_extra    block    in    which    match_limit    is    set,     and         pcre_extra     block    in    which    match_limit    is    set,    and
1944         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
1945         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1946    
1947         The match_limit_recursion field is similar to match_limit, but  instead         The  match_limit_recursion field is similar to match_limit, but instead
1948         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
1949         the depth of recursion. The recursion depth is a  smaller  number  than         the  depth  of  recursion. The recursion depth is a smaller number than
1950         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-
1951         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.
1952    
1953         Limiting the recursion depth limits the amount of  stack  that  can  be         Limiting  the  recursion  depth  limits the amount of stack that can be
1954         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
1955         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
1956    
1957         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
1958         built;  the  default  default  is  the  same  value  as the default for         built; the default default  is  the  same  value  as  the  default  for
1959         match_limit. You can override the default by suppling pcre_exec()  with         match_limit.  You can override the default by suppling pcre_exec() with
1960         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
1961         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
1962         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1963    
1964         The  callout_data  field is used in conjunction with the "callout" fea-         The callout_data field is used in conjunction with the  "callout"  fea-
1965         ture, and is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
1966    
1967         The tables field  is  used  to  pass  a  character  tables  pointer  to         The  tables  field  is  used  to  pass  a  character  tables pointer to
1968         pcre_exec();  this overrides the value that is stored with the compiled         pcre_exec(); this overrides the value that is stored with the  compiled
1969         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
1970         custom  tables  were  supplied to pcre_compile() via its tableptr argu-         custom tables were supplied to pcre_compile() via  its  tableptr  argu-
1971         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
1972         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-
1973         using patterns that have been saved after compiling  with  an  external         using  patterns  that  have been saved after compiling with an external
1974         set  of  tables,  because  the  external tables might be at a different         set of tables, because the external tables  might  be  at  a  different
1975         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address  when  pcre_exec() is called. See the pcreprecompile documenta-
1976         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1977    
1978           If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
1979           set  to  point  to a char * variable. If the pattern contains any back-
1980           tracking control verbs such as (*MARK:NAME), and the execution ends  up
1981           with  a  name  to  pass back, a pointer to the name string (zero termi-
1982           nated) is placed in the variable pointed to  by  the  mark  field.  The
1983           names  are  within  the  compiled pattern; if you wish to retain such a
1984           name you must copy it before freeing the memory of a compiled  pattern.
1985           If  there  is no name to pass back, the variable pointed to by the mark
1986           field set to NULL. For details of the backtracking control  verbs,  see
1987           the section entitled "Backtracking control" in the pcrepattern documen-
1988           tation.
1989    
1990     Option bits for pcre_exec()     Option bits for pcre_exec()
1991    
1992         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.
1993         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,
1994         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,         PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,
1995         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and         PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,  and
1996         PCRE_PARTIAL_HARD.         PCRE_PARTIAL_HARD.
1997    
1998           PCRE_ANCHORED           PCRE_ANCHORED
1999    
2000         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
2001         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
2002         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
2003         unachored at matching time.         unachored at matching time.
2004    
2005           PCRE_BSR_ANYCRLF           PCRE_BSR_ANYCRLF
2006           PCRE_BSR_UNICODE           PCRE_BSR_UNICODE
2007    
2008         These options (which are mutually exclusive) control what the \R escape         These options (which are mutually exclusive) control what the \R escape
2009         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,
2010         or to match any Unicode newline sequence. These  options  override  the         or  to  match  any Unicode newline sequence. These options override the
2011         choice that was made or defaulted when the pattern was compiled.         choice that was made or defaulted when the pattern was compiled.
2012    
2013           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1999  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2016  MATCHING A PATTERN: THE TRADITIONAL FUNC
2016           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
2017           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
2018    
2019         These  options  override  the  newline  definition  that  was chosen or         These options override  the  newline  definition  that  was  chosen  or
2020         defaulted when the pattern was compiled. For details, see the  descrip-         defaulted  when the pattern was compiled. For details, see the descrip-
2021         tion  of  pcre_compile()  above.  During  matching,  the newline choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
2022         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
2023         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
2024         match failure for an unanchored pattern.         match failure for an unanchored pattern.
2025    
2026         When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is         When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
2027         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-
2028         rent position is at a  CRLF  sequence,  and  the  pattern  contains  no         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
2029         explicit  matches  for  CR  or  LF  characters,  the  match position is         explicit matches for  CR  or  LF  characters,  the  match  position  is
2030         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
2031         CRLF.         CRLF.
2032    
2033         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
2034         expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL         expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
2035         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
2036         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.
2037         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-
2038         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-
2039         acter after the first failure.         acter after the first failure.
2040    
2041         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
2042         those characters, or one of the \r or  \n  escape  sequences.  Implicit         those  characters,  or  one  of the \r or \n escape sequences. Implicit
2043         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
2044         LF in the characters that it matches).         LF in the characters that it matches).
2045    
2046         Notwithstanding the above, anomalous effects may still occur when  CRLF         Notwithstanding  the above, anomalous effects may still occur when CRLF
2047         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
2048         pattern.         pattern.
2049    
2050           PCRE_NOTBOL           PCRE_NOTBOL
2051    
2052         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2053         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
2054         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
2055         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
2056         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2057    
2058           PCRE_NOTEOL           PCRE_NOTEOL
2059    
2060         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
2061         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
2062         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
2063         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2064         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
2065         not affect \Z or \z.         not affect \Z or \z.
2066    
2067           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2068    
2069         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
2070         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
2071         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
2072         example, if the pattern         example, if the pattern
2073    
2074           a?b?           a?b?
2075    
2076         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
2077         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
2078         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-
2079         rences of "a" or "b".         rences of "a" or "b".
2080    
2081           PCRE_NOTEMPTY_ATSTART           PCRE_NOTEMPTY_ATSTART
2082    
2083         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
2084         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
2085         anchored, such a match can occur only if the pattern contains \K.         anchored, such a match can occur only if the pattern contains \K.
2086    
2087         Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or
2088         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
2089         match  of  the empty string within its split() function, and when using         match of the empty string within its split() function, and  when  using
2090         the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after         the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after
2091         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-
2092         set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that         set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2093         fails, by advancing the starting offset (see below) and trying an ordi-         fails, by advancing the starting offset (see below) and trying an ordi-
2094         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
2095         in the pcredemo sample program.         in the pcredemo sample program.
2096    
2097           PCRE_NO_START_OPTIMIZE           PCRE_NO_START_OPTIMIZE
2098    
2099         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
2100         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
2101         known  that  a  match must start with a specific character, it searches         known that a match must start with a specific  character,  it  searches
2102         the subject for that character, and fails immediately if it cannot find         the subject for that character, and fails immediately if it cannot find
2103         it,  without actually running the main matching function. When callouts         it, without actually running the main matching function. When  callouts
2104         are in use, these optimizations can cause  them  to  be  skipped.  This         are  in  use,  these  optimizations  can cause them to be skipped. This
2105         option  disables  the  "start-up" optimizations, causing performance to         option disables the "start-up" optimizations,  causing  performance  to
2106         suffer, but ensuring that the callouts do occur.         suffer, but ensuring that the callouts do occur.
2107    
2108           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2109    
2110         When PCRE_UTF8 is set at compile time, the validity of the subject as a         When PCRE_UTF8 is set at compile time, the validity of the subject as a
2111         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8 string is automatically checked when pcre_exec() is  subsequently
2112         called.  The value of startoffset is also checked  to  ensure  that  it         called.   The  value  of  startoffset is also checked to ensure that it
2113         points  to  the start of a UTF-8 character. There is a discussion about         points to the start of a UTF-8 character. There is a  discussion  about
2114         the validity of UTF-8 strings in the section on UTF-8  support  in  the         the  validity  of  UTF-8 strings in the section on UTF-8 support in the
2115         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,         main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,
2116         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-         pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-
2117         tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.         tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
2118    
2119         If  you  already  know that your subject is valid, and you want to skip         If you already know that your subject is valid, and you  want  to  skip
2120         these   checks   for   performance   reasons,   you   can    set    the         these    checks    for   performance   reasons,   you   can   set   the
2121         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
2122         do this for the second and subsequent calls to pcre_exec() if  you  are         do  this  for the second and subsequent calls to pcre_exec() if you are
2123         making  repeated  calls  to  find  all  the matches in a single subject         making repeated calls to find all  the  matches  in  a  single  subject
2124         string. However, you should be  sure  that  the  value  of  startoffset         string.  However,  you  should  be  sure  that the value of startoffset
2125         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is
2126         set, the effect of passing an invalid UTF-8 string as a subject,  or  a         set,  the  effect of passing an invalid UTF-8 string as a subject, or a
2127         value  of startoffset that does not point to the start of a UTF-8 char-         value of startoffset that does not point to the start of a UTF-8  char-
2128         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
2129    
2130           PCRE_PARTIAL_HARD           PCRE_PARTIAL_HARD
2131           PCRE_PARTIAL_SOFT           PCRE_PARTIAL_SOFT
2132    
2133         These options turn on the partial matching feature. For backwards  com-         These  options turn on the partial matching feature. For backwards com-
2134         patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial         patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A  partial
2135         match occurs if the end of the subject string is reached  successfully,         match  occurs if the end of the subject string is reached successfully,
2136         but  there  are not enough subject characters to complete the match. If         but there are not enough subject characters to complete the  match.  If
2137         this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately         this  happens  when  PCRE_PARTIAL_HARD  is set, pcre_exec() immediately
2138         returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,         returns PCRE_ERROR_PARTIAL. Otherwise,  if  PCRE_PARTIAL_SOFT  is  set,
2139         matching continues by testing any other alternatives. Only if they  all         matching  continues by testing any other alternatives. Only if they all
2140         fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).         fail is PCRE_ERROR_PARTIAL returned  (instead  of  PCRE_ERROR_NOMATCH).
2141         The portion of the string that was inspected when the partial match was         The portion of the string that was inspected when the partial match was
2142         found  is  set  as  the first matching string. There is a more detailed         found is set as the first matching string. There  is  a  more  detailed
2143         discussion in the pcrepartial documentation.         discussion in the pcrepartial documentation.
2144    
2145     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2146    
2147         The subject string is passed to pcre_exec() as a pointer in subject,  a         The  subject string is passed to pcre_exec() as a pointer in subject, a
2148         length (in bytes) in length, and a starting byte offset in startoffset.         length (in bytes) in length, and a starting byte offset in startoffset.
2149         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-
2150         acter.  Unlike  the pattern string, the subject may contain binary zero         acter. Unlike the pattern string, the subject may contain  binary  zero
2151         bytes. When the starting offset is zero, the search for a match  starts         bytes.  When the starting offset is zero, the search for a match starts
2152         at  the  beginning  of  the subject, and this is by far the most common         at the beginning of the subject, and this is by  far  the  most  common
2153         case.         case.
2154    
2155         A non-zero starting offset is useful when searching for  another  match         A  non-zero  starting offset is useful when searching for another match
2156         in  the same subject by calling pcre_exec() again after a previous suc-         in the same subject by calling pcre_exec() again after a previous  suc-
2157         cess.  Setting startoffset differs from just passing over  a  shortened         cess.   Setting  startoffset differs from just passing over a shortened
2158         string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins
2159         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2160    
2161           \Biss\B           \Biss\B
2162    
2163         which finds occurrences of "iss" in the middle of  words.  (\B  matches         which  finds  occurrences  of "iss" in the middle of words. (\B matches
2164         only  if  the  current position in the subject is not a word boundary.)         only if the current position in the subject is not  a  word  boundary.)
2165         When applied to the string "Mississipi" the first call  to  pcre_exec()         When  applied  to the string "Mississipi" the first call to pcre_exec()
2166         finds  the  first  occurrence. If pcre_exec() is called again with just         finds the first occurrence. If pcre_exec() is called  again  with  just
2167         the remainder of the subject,  namely  "issipi",  it  does  not  match,         the  remainder  of  the  subject,  namely  "issipi", it does not match,
2168         because \B is always false at the start of the subject, which is deemed         because \B is always false at the start of the subject, which is deemed
2169         to be a word boundary. However, if pcre_exec()  is  passed  the  entire         to  be  a  word  boundary. However, if pcre_exec() is passed the entire
2170         string again, but with startoffset set to 4, it finds the second occur-         string again, but with startoffset set to 4, it finds the second occur-
2171         rence of "iss" because it is able to look behind the starting point  to         rence  of "iss" because it is able to look behind the starting point to
2172         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2173    
2174         If  a  non-zero starting offset is passed when the pattern is anchored,         If a non-zero starting offset is passed when the pattern  is  anchored,
2175         one attempt to match at the given offset is made. This can only succeed         one attempt to match at the given offset is made. This can only succeed
2176         if  the  pattern  does  not require the match to be at the start of the         if the pattern does not require the match to be at  the  start  of  the
2177         subject.         subject.
2178    
2179     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2180    
2181         In general, a pattern matches a certain portion of the subject, and  in         In  general, a pattern matches a certain portion of the subject, and in
2182         addition,  further  substrings  from  the  subject may be picked out by         addition, further substrings from the subject  may  be  picked  out  by
2183         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,
2184         this  is  called "capturing" in what follows, and the phrase "capturing         this is called "capturing" in what follows, and the  phrase  "capturing
2185         subpattern" is used for a fragment of a pattern that picks out  a  sub-         subpattern"  is  used for a fragment of a pattern that picks out a sub-
2186         string.  PCRE  supports several other kinds of parenthesized subpattern         string. PCRE supports several other kinds of  parenthesized  subpattern
2187         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2188    
2189         Captured substrings are returned to the caller via a vector of integers         Captured substrings are returned to the caller via a vector of integers
2190         whose  address is passed in ovector. The number of elements in the vec-         whose address is passed in ovector. The number of elements in the  vec-
2191         tor is passed in ovecsize, which must be a non-negative  number.  Note:         tor  is  passed in ovecsize, which must be a non-negative number. Note:
2192         this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2193    
2194         The  first  two-thirds of the vector is used to pass back captured sub-         The first two-thirds of the vector is used to pass back  captured  sub-
2195         strings, each substring using a pair of integers. The  remaining  third         strings,  each  substring using a pair of integers. The remaining third
2196         of  the  vector is used as workspace by pcre_exec() while matching cap-         of the vector is used as workspace by pcre_exec() while  matching  cap-
2197         turing subpatterns, and is not available for passing back  information.         turing  subpatterns, and is not available for passing back information.
2198         The  number passed in ovecsize should always be a multiple of three. If         The number passed in ovecsize should always be a multiple of three.  If
2199         it is not, it is rounded down.         it is not, it is rounded down.
2200    
2201         When a match is successful, information about  captured  substrings  is         When  a  match  is successful, information about captured substrings is
2202         returned  in  pairs  of integers, starting at the beginning of ovector,         returned in pairs of integers, starting at the  beginning  of  ovector,
2203         and continuing up to two-thirds of its length at the  most.  The  first         and  continuing  up  to two-thirds of its length at the most. The first
2204         element  of  each pair is set to the byte offset of the first character         element of each pair is set to the byte offset of the  first  character
2205         in a substring, and the second is set to the byte offset of  the  first         in  a  substring, and the second is set to the byte offset of the first
2206         character  after  the end of a substring. Note: these values are always         character after the end of a substring. Note: these values  are  always
2207         byte offsets, even in UTF-8 mode. They are not character counts.         byte offsets, even in UTF-8 mode. They are not character counts.
2208    
2209         The first pair of integers, ovector[0]  and  ovector[1],  identify  the         The  first  pair  of  integers, ovector[0] and ovector[1], identify the
2210         portion  of  the subject string matched by the entire pattern. The next         portion of the subject string matched by the entire pattern.  The  next
2211         pair is used for the first capturing subpattern, and so on.  The  value         pair  is  used for the first capturing subpattern, and so on. The value
2212         returned by pcre_exec() is one more than the highest numbered pair that         returned by pcre_exec() is one more than the highest numbered pair that
2213         has been set.  For example, if two substrings have been  captured,  the         has  been  set.  For example, if two substrings have been captured, the
2214         returned  value is 3. If there are no capturing subpatterns, the return         returned value is 3. If there are no capturing subpatterns, the  return
2215         value from a successful match is 1, indicating that just the first pair         value from a successful match is 1, indicating that just the first pair
2216         of offsets has been set.         of offsets has been set.
2217    
2218         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2219         of the string that it matched that is returned.         of the string that it matched that is returned.
2220    
2221         If the vector is too small to hold all the captured substring  offsets,         If  the vector is too small to hold all the captured substring offsets,
2222         it is used as far as possible (up to two-thirds of its length), and the         it is used as far as possible (up to two-thirds of its length), and the
2223         function returns a value of zero. If the substring offsets are  not  of         function  returns  a value of zero. If the substring offsets are not of
2224         interest,  pcre_exec()  may  be  called with ovector passed as NULL and         interest, pcre_exec() may be called with ovector  passed  as  NULL  and
2225         ovecsize as zero. However, if the pattern contains back references  and         ovecsize  as zero. However, if the pattern contains back references and
2226         the  ovector is not big enough to remember the related substrings, PCRE         the ovector is not big enough to remember the related substrings,  PCRE
2227         has to get additional memory for use during matching. Thus it  is  usu-         has  to  get additional memory for use during matching. Thus it is usu-
2228         ally advisable to supply an ovector.         ally advisable to supply an ovector.
2229    
2230         The pcre_fullinfo() function can be used to find out how many capturing         The pcre_fullinfo() function can be used to find out how many capturing
2231         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns  there  are  in  a  compiled pattern. The smallest size for
2232         ovector  that  will allow for n captured substrings, in addition to the         ovector that will allow for n captured substrings, in addition  to  the
2233         offsets of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
2234    
2235         It is possible for capturing subpattern number n+1 to match  some  part         It  is  possible for capturing subpattern number n+1 to match some part
2236         of the subject when subpattern n has not been used at all. For example,         of the subject when subpattern n has not been used at all. For example,
2237         if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the         if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the
2238         return from the function is 4, and subpatterns 1 and 3 are matched, but         return from the function is 4, and subpatterns 1 and 3 are matched, but
2239         2 is not. When this happens, both values in  the  offset  pairs  corre-         2  is  not.  When  this happens, both values in the offset pairs corre-
2240         sponding to unused subpatterns are set to -1.         sponding to unused subpatterns are set to -1.
2241    
2242         Offset  values  that correspond to unused subpatterns at the end of the         Offset values that correspond to unused subpatterns at the end  of  the
2243         expression are also set to -1. For example,  if  the  string  "abc"  is         expression  are  also  set  to  -1. For example, if the string "abc" is
2244         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not         matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are  not
2245         matched. The return from the function is 2, because  the  highest  used         matched.  The  return  from the function is 2, because the highest used
2246         capturing subpattern number is 1. However, you can refer to the offsets         capturing subpattern number is 1. However, you can refer to the offsets
2247         for the second and third capturing subpatterns if  you  wish  (assuming         for  the  second  and third capturing subpatterns if you wish (assuming
2248         the vector is large enough, of course).         the vector is large enough, of course).
2249    
2250         Some  convenience  functions  are  provided for extracting the captured         Some convenience functions are provided  for  extracting  the  captured
2251         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
2252    
2253     Error return values from pcre_exec()     Error return values from pcre_exec()
2254    
2255         If pcre_exec() fails, it returns a negative number. The  following  are         If  pcre_exec()  fails, it returns a negative number. The following are
2256         defined in the header file:         defined in the header file:
2257    
2258           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 2244  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2261  MATCHING A PATTERN: THE TRADITIONAL FUNC
2261    
2262           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2263    
2264         Either  code  or  subject  was  passed as NULL, or ovector was NULL and         Either code or subject was passed as NULL,  or  ovector  was  NULL  and
2265         ovecsize was not zero.         ovecsize was not zero.
2266    
2267           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 2253  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2270  MATCHING A PATTERN: THE TRADITIONAL FUNC
2270    
2271           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2272    
2273         PCRE stores a 4-byte "magic number" at the start of the compiled  code,         PCRE  stores a 4-byte "magic number" at the start of the compiled code,
2274         to catch the case when it is passed a junk pointer and to detect when a         to catch the case when it is passed a junk pointer and to detect when a
2275         pattern that was compiled in an environment of one endianness is run in         pattern that was compiled in an environment of one endianness is run in
2276         an  environment  with the other endianness. This is the error that PCRE         an environment with the other endianness. This is the error  that  PCRE
2277         gives when the magic number is not present.         gives when the magic number is not present.
2278    
2279           PCRE_ERROR_UNKNOWN_OPCODE (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2280    
2281         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2282         compiled  pattern.  This  error  could be caused by a bug in PCRE or by         compiled pattern. This error could be caused by a bug  in  PCRE  or  by
2283         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2284    
2285           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2286    
2287         If a pattern contains back references, but the ovector that  is  passed         If  a  pattern contains back references, but the ovector that is passed
2288         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2289         PCRE gets a block of memory at the start of matching to  use  for  this         PCRE  gets  a  block of memory at the start of matching to use for this
2290         purpose.  If the call via pcre_malloc() fails, this error is given. The         purpose. If the call via pcre_malloc() fails, this error is given.  The
2291         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2292    
2293           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2294    
2295         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This  error is used by the pcre_copy_substring(), pcre_get_substring(),
2296         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2297         returned by pcre_exec().         returned by pcre_exec().
2298    
2299           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2300    
2301         The backtracking limit, as specified by  the  match_limit  field  in  a         The  backtracking  limit,  as  specified  by the match_limit field in a
2302         pcre_extra  structure  (or  defaulted) was reached. See the description         pcre_extra structure (or defaulted) was reached.  See  the  description
2303         above.         above.
2304    
2305           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2306    
2307         This error is never generated by pcre_exec() itself. It is provided for         This error is never generated by pcre_exec() itself. It is provided for
2308         use  by  callout functions that want to yield a distinctive error code.         use by callout functions that want to yield a distinctive  error  code.
2309         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2310    
2311           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2312    
2313         A string that contains an invalid UTF-8 byte sequence was passed  as  a         A  string  that contains an invalid UTF-8 byte sequence was passed as a
2314         subject.         subject.
2315    
2316           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2317    
2318         The UTF-8 byte sequence that was passed as a subject was valid, but the         The UTF-8 byte sequence that was passed as a subject was valid, but the
2319         value of startoffset did not point to the beginning of a UTF-8  charac-         value  of startoffset did not point to the beginning of a UTF-8 charac-
2320         ter.         ter.
2321    
2322           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2323    
2324         The  subject  string did not match, but it did match partially. See the         The subject string did not match, but it did match partially.  See  the
2325         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2326    
2327           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2328    
2329         This code is no longer in  use.  It  was  formerly  returned  when  the         This  code  is  no  longer  in  use.  It was formerly returned when the
2330         PCRE_PARTIAL  option  was used with a compiled pattern containing items         PCRE_PARTIAL option was used with a compiled pattern  containing  items
2331         that were  not  supported  for  partial  matching.  From  release  8.00         that  were  not  supported  for  partial  matching.  From  release 8.00
2332         onwards, there are no restrictions on partial matching.         onwards, there are no restrictions on partial matching.
2333    
2334           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2335    
2336         An  unexpected  internal error has occurred. This error could be caused         An unexpected internal error has occurred. This error could  be  caused
2337         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2338    
2339           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
# Line 2326  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2343  MATCHING A PATTERN: THE TRADITIONAL FUNC
2343           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2344    
2345         The internal recursion limit, as specified by the match_limit_recursion         The internal recursion limit, as specified by the match_limit_recursion
2346         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field in a pcre_extra structure (or defaulted)  was  reached.  See  the
2347         description above.         description above.
2348    
2349           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
# Line 2349  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2366  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2366         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2367              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2368    
2369         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2370         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2371         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2372         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2373         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2374         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2375         substrings.         substrings.
2376    
2377         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2378         a  further zero added on the end, but the result is not, of course, a C         a further zero added on the end, but the result is not, of course, a  C
2379         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2380         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2381         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2382         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2383         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2384    
2385         The first three arguments are the same for all  three  of  these  func-         The  first  three  arguments  are the same for all three of these func-
2386         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2387         matched, ovector is a pointer to the vector of integer offsets that was         matched, ovector is a pointer to the vector of integer offsets that was
2388         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2389         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2390         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2391         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2392         it  ran out of space in ovector, the value passed as stringcount should         it ran out of space in ovector, the value passed as stringcount  should
2393         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2394    
2395         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2396         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2397         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2398         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2399         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2400         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2401         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2402         The  yield  of  the function is the length of the string, not including         The yield of the function is the length of the  string,  not  including
2403         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2404    
2405           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2406    
2407         The buffer was too small for pcre_copy_substring(), or the  attempt  to         The  buffer  was too small for pcre_copy_substring(), or the attempt to
2408         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2409    
2410           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2411    
2412         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2413    
2414         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2415         strings and builds a list of pointers to them. All this is  done  in  a         strings  and  builds  a list of pointers to them. All this is done in a
2416         single block of memory that is obtained via pcre_malloc. The address of         single block of memory that is obtained via pcre_malloc. The address of
2417         the memory block is returned via listptr, which is also  the  start  of         the  memory  block  is returned via listptr, which is also the start of
2418         the  list  of  string pointers. The end of the list is marked by a NULL         the list of string pointers. The end of the list is marked  by  a  NULL
2419         pointer. The yield of the function is zero if all  went  well,  or  the         pointer.  The  yield  of  the function is zero if all went well, or the
2420         error code         error code
2421    
2422           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2423    
2424         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2425    
2426         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2427         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2428         the  subject, but subpattern n has not been used at all, they return an         the subject, but subpattern n has not been used at all, they return  an
2429         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2430         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2431         tive for unset substrings.         tive for unset substrings.
2432    
2433         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2434         string_list()  can  be  used  to free the memory returned by a previous         string_list() can be used to free the memory  returned  by  a  previous
2435         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2436         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2437         pcre_free, which of course could be called directly from a  C  program.         pcre_free,  which  of course could be called directly from a C program.
2438         However,  PCRE is used in some situations where it is linked via a spe-         However, PCRE is used in some situations where it is linked via a  spe-
2439         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2440         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free directly; it is for these cases that the functions  are  pro-
2441         vided.         vided.
2442    
2443    
# Line 2439  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2456  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2456              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2457              const char **stringptr);              const char **stringptr);
2458    
2459         To extract a substring by name, you first have to find associated  num-         To  extract a substring by name, you first have to find associated num-
2460         ber.  For example, for this pattern         ber.  For example, for this pattern
2461    
2462           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2448  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2465  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2465         be unique (PCRE_DUPNAMES was not set), you can find the number from the         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2466         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2467         piled pattern, and the second is the name. The yield of the function is         piled pattern, and the second is the name. The yield of the function is
2468         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2469         subpattern of that name.         subpattern of that name.
2470    
2471         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2472         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2473         are also two functions that do the whole job.         are also two functions that do the whole job.
2474    
2475         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2476         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2477         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2478         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2479         differences:         differences:
2480    
2481         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2482         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2483         to the compiled pattern. This is needed in order to gain access to  the         to  the compiled pattern. This is needed in order to gain access to the
2484         name-to-number translation table.         name-to-number translation table.
2485    
2486         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2487         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2488         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2489         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2490    
2491         Warning: If the pattern uses the (?| feature to set up multiple subpat-         Warning: If the pattern uses the (?| feature to set up multiple subpat-
2492         terns  with  the  same number, as described in the section on duplicate         terns with the same number, as described in the  section  on  duplicate
2493         subpattern numbers in the pcrepattern page, you  cannot  use  names  to         subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2494         distinguish  the  different subpatterns, because names are not included         distinguish the different subpatterns, because names are  not  included
2495         in the compiled code. The matching process uses only numbers. For  this         in  the compiled code. The matching process uses only numbers. For this
2496         reason,  the  use of different names for subpatterns of the same number         reason, the use of different names for subpatterns of the  same  number
2497         causes an error at compile time.         causes an error at compile time.
2498    
2499    
# Line 2485  DUPLICATE SUBPATTERN NAMES Line 2502  DUPLICATE SUBPATTERN NAMES
2502         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2503              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2504    
2505         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2506         subpatterns  are not required to be unique. (Duplicate names are always         subpatterns are not required to be unique. (Duplicate names are  always
2507         allowed for subpatterns with the same number, created by using the  (?|         allowed  for subpatterns with the same number, created by using the (?|
2508         feature.  Indeed,  if  such subpatterns are named, they are required to         feature. Indeed, if such subpatterns are named, they  are  required  to
2509         use the same names.)         use the same names.)
2510    
2511         Normally, patterns with duplicate names are such that in any one match,         Normally, patterns with duplicate names are such that in any one match,
2512         only  one of the named subpatterns participates. An example is shown in         only one of the named subpatterns participates. An example is shown  in
2513         the pcrepattern documentation.         the pcrepattern documentation.
2514    
2515         When   duplicates   are   present,   pcre_copy_named_substring()    and         When    duplicates   are   present,   pcre_copy_named_substring()   and
2516         pcre_get_named_substring()  return the first substring corresponding to         pcre_get_named_substring() return the first substring corresponding  to
2517         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING         the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2518         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2519         function returns one of the numbers that are associated with the  name,         function  returns one of the numbers that are associated with the name,
2520         but it is not defined which it is.         but it is not defined which it is.
2521    
2522         If  you want to get full details of all captured substrings for a given         If you want to get full details of all captured substrings for a  given
2523         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
2524         first argument is the compiled pattern, and the second is the name. The         first argument is the compiled pattern, and the second is the name. The
2525         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
2526         function. After it has run, they point to the first and last entries in         function. After it has run, they point to the first and last entries in
2527         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
2528         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2529         there are none. The format of the table is described above in the  sec-         there  are none. The format of the table is described above in the sec-
2530         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a  pattern.   Given  all  the  relevant
2531         entries for the name, you can extract each of their numbers, and  hence         entries  for the name, you can extract each of their numbers, and hence
2532         the captured data, if any.         the captured data, if any.
2533    
2534    
2535  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2536    
2537         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
2538         which stops when it finds the first match, starting at a given point in         which stops when it finds the first match, starting at a given point in
2539         the  subject.  If you want to find all possible matches, or the longest         the subject. If you want to find all possible matches, or  the  longest
2540         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
2541         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
2542         need to find all possible matches, you can kludge it up by  making  use         need  to  find all possible matches, you can kludge it up by making use
2543         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2544         tation.         tation.
2545    
2546         What you have to do is to insert a callout right at the end of the pat-         What you have to do is to insert a callout right at the end of the pat-
2547         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
2548         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2549         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
2550         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2551    
2552    
# Line 2540  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2557  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2557              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2558              int *workspace, int wscount);              int *workspace, int wscount);
2559    
2560         The function pcre_dfa_exec()  is  called  to  match  a  subject  string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2561         against  a  compiled pattern, using a matching algorithm that scans the         against a compiled pattern, using a matching algorithm that  scans  the
2562         subject string just once, and does not backtrack.  This  has  different         subject  string  just  once, and does not backtrack. This has different
2563         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics to the normal algorithm, and  is  not  compatible  with
2564         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2565         theless,  there are times when this kind of matching can be useful. For         theless, there are times when this kind of matching can be useful.  For
2566         a discussion of the two matching algorithms, and  a  list  of  features         a  discussion  of  the  two matching algorithms, and a list of features
2567         that  pcre_dfa_exec() does not support, see the pcrematching documenta-         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2568         tion.         tion.
2569    
2570         The arguments for the pcre_dfa_exec() function  are  the  same  as  for         The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2571         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
2572         ent way, and this is described below. The other  common  arguments  are         ent  way,  and  this is described below. The other common arguments are
2573         used  in  the  same way as for pcre_exec(), so their description is not         used in the same way as for pcre_exec(), so their  description  is  not
2574         repeated here.         repeated here.
2575    
2576         The two additional arguments provide workspace for  the  function.  The         The  two  additional  arguments provide workspace for the function. The
2577         workspace  vector  should  contain at least 20 elements. It is used for         workspace vector should contain at least 20 elements. It  is  used  for
2578         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2579         workspace  will  be  needed for patterns and subjects where there are a         workspace will be needed for patterns and subjects where  there  are  a
2580         lot of potential matches.         lot of potential matches.
2581    
2582         Here is an example of a simple call to pcre_dfa_exec():         Here is an example of a simple call to pcre_dfa_exec():
# Line 2581  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2598  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2598    
2599     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2600    
2601         The unused bits of the options argument  for  pcre_dfa_exec()  must  be         The  unused  bits  of  the options argument for pcre_dfa_exec() must be
2602         zero.  The  only  bits  that  may  be  set are PCRE_ANCHORED, PCRE_NEW-         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2603         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2604         PCRE_NOTEMPTY_ATSTART, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PAR-         PCRE_NOTEMPTY_ATSTART, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PAR-
2605         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last         TIAL_SOFT,  PCRE_DFA_SHORTEST,  and  PCRE_DFA_RESTART. All but the last
2606         four  of  these  are  exactly  the  same  as  for pcre_exec(), so their         four of these are  exactly  the  same  as  for  pcre_exec(),  so  their
2607         description is not repeated here.         description is not repeated here.
2608    
2609           PCRE_PARTIAL_HARD           PCRE_PARTIAL_HARD
2610           PCRE_PARTIAL_SOFT           PCRE_PARTIAL_SOFT
2611    
2612         These have the same general effect as they do for pcre_exec(), but  the         These  have the same general effect as they do for pcre_exec(), but the
2613         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for         details are slightly  different.  When  PCRE_PARTIAL_HARD  is  set  for
2614         pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of  the  sub-         pcre_dfa_exec(),  it  returns PCRE_ERROR_PARTIAL if the end of the sub-
2615         ject  is  reached  and there is still at least one matching possibility         ject is reached and there is still at least  one  matching  possibility
2616         that requires additional characters. This happens even if some complete         that requires additional characters. This happens even if some complete
2617         matches have also been found. When PCRE_PARTIAL_SOFT is set, the return         matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2618         code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end         code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2619         of  the  subject  is  reached, there have been no complete matches, but         of the subject is reached, there have been  no  complete  matches,  but
2620         there is still at least one matching possibility. The  portion  of  the         there  is  still  at least one matching possibility. The portion of the
2621         string  that  was inspected when the longest partial match was found is         string that was inspected when the longest partial match was  found  is
2622         set as the first matching string in both cases.         set as the first matching string in both cases.
2623    
2624           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2625    
2626         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to
2627         stop as soon as it has found one match. Because of the way the alterna-         stop as soon as it has found one match. Because of the way the alterna-
2628         tive algorithm works, this is necessarily the shortest  possible  match         tive  algorithm  works, this is necessarily the shortest possible match
2629         at the first possible matching point in the subject string.         at the first possible matching point in the subject string.
2630    
2631           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2632    
2633         When pcre_dfa_exec() returns a partial match, it is possible to call it         When pcre_dfa_exec() returns a partial match, it is possible to call it
2634         again, with additional subject characters, and have  it  continue  with         again,  with  additional  subject characters, and have it continue with
2635         the  same match. The PCRE_DFA_RESTART option requests this action; when         the same match. The PCRE_DFA_RESTART option requests this action;  when
2636         it is set, the workspace and wscount options must  reference  the  same         it  is  set,  the workspace and wscount options must reference the same
2637         vector  as  before  because data about the match so far is left in them         vector as before because data about the match so far is  left  in  them
2638         after a partial match. There is more discussion of this facility in the         after a partial match. There is more discussion of this facility in the
2639         pcrepartial documentation.         pcrepartial documentation.
2640    
2641     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2642    
2643         When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-         When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-
2644         string in the subject. Note, however, that all the matches from one run         string in the subject. Note, however, that all the matches from one run
2645         of  the  function  start  at the same point in the subject. The shorter         of the function start at the same point in  the  subject.  The  shorter
2646         matches are all initial substrings of the longer matches. For  example,         matches  are all initial substrings of the longer matches. For example,
2647         if the pattern         if the pattern
2648    
2649           <.*>           <.*>
# Line 2641  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2658  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2658           <something> <something else>           <something> <something else>
2659           <something> <something else> <something further>           <something> <something else> <something further>
2660    
2661         On  success,  the  yield of the function is a number greater than zero,         On success, the yield of the function is a number  greater  than  zero,
2662         which is the number of matched substrings.  The  substrings  themselves         which  is  the  number of matched substrings. The substrings themselves
2663         are  returned  in  ovector. Each string uses two elements; the first is         are returned in ovector. Each string uses two elements;  the  first  is
2664         the offset to the start, and the second is the offset to  the  end.  In         the  offset  to  the start, and the second is the offset to the end. In
2665         fact,  all  the  strings  have the same start offset. (Space could have         fact, all the strings have the same start  offset.  (Space  could  have
2666         been saved by giving this only once, but it was decided to retain  some         been  saved by giving this only once, but it was decided to retain some
2667         compatibility  with  the  way pcre_exec() returns data, even though the         compatibility with the way pcre_exec() returns data,  even  though  the
2668         meaning of the strings is different.)         meaning of the strings is different.)
2669    
2670         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
2671         est  matching  string is given first. If there were too many matches to         est matching string is given first. If there were too many  matches  to
2672         fit into ovector, the yield of the function is zero, and the vector  is         fit  into ovector, the yield of the function is zero, and the vector is
2673         filled with the longest matches.         filled with the longest matches.
2674    
2675     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2676    
2677         The  pcre_dfa_exec()  function returns a negative number when it fails.         The pcre_dfa_exec() function returns a negative number when  it  fails.
2678         Many of the errors are the same  as  for  pcre_exec(),  and  these  are         Many  of  the  errors  are  the  same as for pcre_exec(), and these are
2679         described  above.   There are in addition the following errors that are         described above.  There are in addition the following errors  that  are
2680         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2681    
2682           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2683    
2684         This return is given if pcre_dfa_exec() encounters an item in the  pat-         This  return is given if pcre_dfa_exec() encounters an item in the pat-
2685         tern  that  it  does not support, for instance, the use of \C or a back         tern that it does not support, for instance, the use of \C  or  a  back
2686         reference.         reference.
2687    
2688           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2689    
2690         This return is given if pcre_dfa_exec()  encounters  a  condition  item         This  return  is  given  if pcre_dfa_exec() encounters a condition item
2691         that  uses  a back reference for the condition, or a test for recursion         that uses a back reference for the condition, or a test  for  recursion
2692         in a specific group. These are not supported.         in a specific group. These are not supported.
2693    
2694           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2695    
2696         This return is given if pcre_dfa_exec() is called with an  extra  block         This  return  is given if pcre_dfa_exec() is called with an extra block
2697         that contains a setting of the match_limit field. This is not supported         that contains a setting of the match_limit field. This is not supported
2698         (it is meaningless).         (it is meaningless).
2699    
2700           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2701    
2702         This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the         This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the
2703         workspace vector.         workspace vector.
2704    
2705           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2706    
2707         When  a  recursive subpattern is processed, the matching function calls         When a recursive subpattern is processed, the matching  function  calls
2708         itself recursively, using private vectors for  ovector  and  workspace.         itself  recursively,  using  private vectors for ovector and workspace.
2709         This  error  is  given  if  the output vector is not large enough. This         This error is given if the output vector  is  not  large  enough.  This
2710         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2711    
2712    
2713  SEE ALSO  SEE ALSO
2714    
2715         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
2716         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2717    
2718    
# Line 2708  AUTHOR Line 2725  AUTHOR
2725    
2726  REVISION  REVISION
2727    
2728         Last updated: 03 October 2009         Last updated: 26 March 2010
2729         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
2730  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2731    
2732    
# Line 5144  BACKTRACKING CONTROL Line 5161  BACKTRACKING CONTROL
5161         tested.         tested.
5162    
5163         The  new verbs make use of what was previously invalid syntax: an open-         The  new verbs make use of what was previously invalid syntax: an open-
5164         ing parenthesis followed by an asterisk. In Perl, they are generally of         ing parenthesis followed by an asterisk. They are generally of the form
5165         the form (*VERB:ARG) but PCRE does not support the use of arguments, so         (*VERB)  or (*VERB:NAME). Some may take either form, with differing be-
5166         its general form is just (*VERB). Any number of these verbs  may  occur         haviour, depending on whether or not an argument is present. An name is
5167         in a pattern. There are two kinds:         a  sequence  of letters, digits, and underscores. If the name is empty,
5168           that is, if the closing parenthesis immediately follows the colon,  the
5169           effect is as if the colon were not there. Any number of these verbs may
5170           occur in a pattern.
5171    
5172           PCRE contains some optimizations that are used to speed up matching  by
5173           running some checks at the start of each match attempt. For example, it
5174           may know the minimum length of matching subject, or that  a  particular
5175           character  must  be present. When one of these optimizations suppresses
5176           the running of a match, any included backtracking verbs  will  not,  of
5177           course, be processed. You can suppress the start-of-match optimizations
5178           by setting the PCRE_NO_START_OPTIMIZE option when calling pcre_exec().
5179    
5180     Verbs that act immediately     Verbs that act immediately
5181    
5182         The following verbs act as soon as they are encountered:         The following verbs act as soon as they are encountered. They  may  not
5183           be followed by a name.
5184    
5185            (*ACCEPT)            (*ACCEPT)
5186    
# Line 5180  BACKTRACKING CONTROL Line 5209  BACKTRACKING CONTROL
5209         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
5210         before each backtrack happens (in this example, 10 times).         before each backtrack happens (in this example, 10 times).
5211    
5212       Recording which path was taken
5213    
5214           There is one verb whose main purpose  is  to  track  how  a  match  was
5215           arrived  at,  though  it  also  has a secondary use in conjunction with
5216           advancing the match starting point (see (*SKIP) below).
5217    
5218             (*MARK:NAME) or (*:NAME)
5219    
5220           A name is always  required  with  this  verb.  There  may  be  as  many
5221           instances  of  (*MARK) as you like in a pattern, and their names do not
5222           have to be unique.
5223    
5224           When a match succeeds, the name  of  the  last-encountered  (*MARK)  is
5225           passed  back  to  the  caller  via  the  pcre_extra  data structure, as
5226           described in the section on pcre_extra in the pcreapi documentation. No
5227           data  is  returned  for a partial match. Here is an example of pcretest
5228           output, where the /K modifier requests the retrieval and outputting  of
5229           (*MARK) data:
5230    
5231             /X(*MARK:A)Y|X(*MARK:B)Z/K
5232             XY
5233              0: XY
5234             MK: A
5235             XZ
5236              0: XZ
5237             MK: B
5238    
5239           The (*MARK) name is tagged with "MK:" in this output, and in this exam-
5240           ple it indicates which of the two alternatives matched. This is a  more
5241           efficient  way of obtaining this information than putting each alterna-
5242           tive in its own capturing parentheses.
5243    
5244           A name may also be returned after a failed  match  if  the  final  path
5245           through  the  pattern involves (*MARK). However, unless (*MARK) used in
5246           conjunction with (*COMMIT), this is unlikely to  happen  for  an  unan-
5247           chored pattern because, as the starting point for matching is advanced,
5248           the final check is often with an empty string, causing a failure before
5249           (*MARK) is reached. For example:
5250    
5251             /X(*MARK:A)Y|X(*MARK:B)Z/K
5252             XP
5253             No match
5254    
5255           There are three potential starting points for this match (starting with
5256           X, starting with P, and with  an  empty  string).  If  the  pattern  is
5257           anchored, the result is different:
5258    
5259             /^X(*MARK:A)Y|^X(*MARK:B)Z/K
5260             XP
5261             No match, mark = B
5262    
5263           PCRE's  start-of-match  optimizations can also interfere with this. For
5264           example, if, as a result of a call to pcre_study(), it knows the  mini-
5265           mum  subject  length for a match, a shorter subject will not be scanned
5266           at all.
5267    
5268           Note that similar anomalies (though different in detail) exist in Perl,
5269           no  doubt  for the same reasons. The use of (*MARK) data after a failed
5270           match of an unanchored pattern is not recommended, unless (*COMMIT)  is
5271           involved.
5272    
5273     Verbs that act after backtracking     Verbs that act after backtracking
5274    
5275         The following verbs do nothing when they are encountered. Matching con-         The following verbs do nothing when they are encountered. Matching con-
5276         tinues  with what follows, but if there is no subsequent match, a fail-         tinues with what follows, but if there is no subsequent match,  causing
5277         ure is forced.  The verbs  differ  in  exactly  what  kind  of  failure         a  backtrack  to  the  verb, a failure is forced. That is, backtracking
5278         occurs.         cannot pass to the left of the verb. However, when one of  these  verbs
5279           appears  inside  an atomic group, its effect is confined to that group,
5280           because once the group has been matched, there is never any  backtrack-
5281           ing  into  it.  In  this situation, backtracking can "jump back" to the
5282           left of the entire atomic group. (Remember also, as stated above,  that
5283           this localization also applies in subroutine calls and assertions.)
5284    
5285           These  verbs  differ  in exactly what kind of failure occurs when back-
5286           tracking reaches them.
5287    
5288           (*COMMIT)           (*COMMIT)
5289    
5290         This  verb  causes  the whole match to fail outright if the rest of the         This verb, which may not be followed by a name, causes the whole  match
5291         pattern does not match. Even if the pattern is unanchored,  no  further         to fail outright if the rest of the pattern does not match. Even if the
5292         attempts  to  find  a match by advancing the starting point take place.         pattern is unanchored, no further attempts to find a match by advancing
5293         Once (*COMMIT) has been passed, pcre_exec() is committed to  finding  a         the  starting  point  take  place.  Once  (*COMMIT)  has  been  passed,
5294         match at the current starting point, or not at all. For example:         pcre_exec() is committed to finding a match  at  the  current  starting
5295           point, or not at all. For example:
5296    
5297           a+(*COMMIT)b           a+(*COMMIT)b
5298    
5299         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
5300         of dynamic anchor, or "I've started, so I must finish."         of dynamic anchor, or "I've started, so I must finish." The name of the
5301           most  recently passed (*MARK) in the path is passed back when (*COMMIT)
5302           (*PRUNE)         forces a match failure.
5303    
5304         This verb causes the match to fail at the current position if the  rest         Note that (*COMMIT) at the start of a pattern is not  the  same  as  an
5305         of the pattern does not match. If the pattern is unanchored, the normal         anchor,  unless  PCRE's start-of-match optimizations are turned off, as
5306         "bumpalong" advance to the next starting character then happens.  Back-         shown in this pcretest example:
5307         tracking  can  occur as usual to the left of (*PRUNE), or when matching  
5308         to the right of (*PRUNE), but if there is no match to the right,  back-           /(*COMMIT)abc/
5309         tracking  cannot  cross (*PRUNE).  In simple cases, the use of (*PRUNE)           xyzabc
5310         is just an alternative to an atomic group or possessive quantifier, but            0: abc
5311         there  are  some uses of (*PRUNE) that cannot be expressed in any other           xyzabc\Y
5312         way.           No match
5313    
5314           PCRE knows that any match must start  with  "a",  so  the  optimization
5315           skips  along the subject to "a" before running the first match attempt,
5316           which succeeds. When the optimization is disabled by the \Y  escape  in
5317           the second subject, the match starts at "x" and so the (*COMMIT) causes
5318           it to fail without trying any other starting points.
5319    
5320             (*PRUNE) or (*PRUNE:NAME)
5321    
5322           This verb causes the match to fail at the current starting position  in
5323           the  subject  if the rest of the pattern does not match. If the pattern
5324           is unanchored, the normal "bumpalong"  advance  to  the  next  starting
5325           character  then happens. Backtracking can occur as usual to the left of
5326           (*PRUNE), before it is reached,  or  when  matching  to  the  right  of
5327           (*PRUNE),  but  if  there is no match to the right, backtracking cannot
5328           cross (*PRUNE). In simple cases, the use of (*PRUNE) is just an  alter-
5329           native  to an atomic group or possessive quantifier, but there are some
5330           uses of (*PRUNE) that cannot be expressed in any other way.  The behav-
5331           iour  of  (*PRUNE:NAME)  is  the  same as (*MARK:NAME)(*PRUNE) when the
5332           match fails completely; the name is passed back if this  is  the  final
5333           attempt.   (*PRUNE:NAME)  does  not  pass back a name if the match suc-
5334           ceeds. In an anchored pattern (*PRUNE) has the same  effect  as  (*COM-
5335           MIT).
5336    
5337           (*SKIP)           (*SKIP)
5338    
5339         This verb is like (*PRUNE), except that if the pattern  is  unanchored,         This  verb, when given without a name, is like (*PRUNE), except that if
5340         the  "bumpalong" advance is not to the next character, but to the posi-         the pattern is unanchored, the "bumpalong" advance is not to  the  next
5341         tion in the subject where (*SKIP) was  encountered.  (*SKIP)  signifies         character, but to the position in the subject where (*SKIP) was encoun-
5342         that  whatever  text  was  matched leading up to it cannot be part of a         tered. (*SKIP) signifies that whatever text was matched leading  up  to
5343         successful match. Consider:         it cannot be part of a successful match. Consider:
5344    
5345           a+(*SKIP)b           a+(*SKIP)b
5346    
5347         If the subject is "aaaac...",  after  the  first  match  attempt  fails         If  the  subject  is  "aaaac...",  after  the first match attempt fails
5348         (starting  at  the  first  character in the string), the starting point         (starting at the first character in the  string),  the  starting  point
5349         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-
5350         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
5351         suppress backtracking  during  the  first  match  attempt,  the  second         suppress  backtracking  during  the  first  match  attempt,  the second
5352         attempt  would  start at the second character instead of skipping on to         attempt would start at the second character instead of skipping  on  to
5353         "c".         "c".
5354    
5355           (*THEN)           (*SKIP:NAME)
5356    
5357           When  (*SKIP) has an associated name, its behaviour is modified. If the
5358           following pattern fails to match, the previous path through the pattern
5359           is  searched for the most recent (*MARK) that has the same name. If one
5360           is found, the "bumpalong" advance is to the subject position that  cor-
5361           responds  to  that (*MARK) instead of to where (*SKIP) was encountered.
5362           If no (*MARK) with a matching name is found, normal "bumpalong" of  one
5363           character happens (the (*SKIP) is ignored).
5364    
5365             (*THEN) or (*THEN:NAME)
5366    
5367         This verb causes a skip to the next alternation if the rest of the pat-         This verb causes a skip to the next alternation if the rest of the pat-
5368         tern does not match. That is, it cancels pending backtracking, but only         tern does not match. That is, it cancels pending backtracking, but only
5369         within the current alternation. Its name  comes  from  the  observation         within  the  current  alternation.  Its name comes from the observation
5370         that it can be used for a pattern-based if-then-else block:         that it can be used for a pattern-based if-then-else block:
5371    
5372           ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ...           ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ...
5373    
5374         If  the COND1 pattern matches, FOO is tried (and possibly further items         If the COND1 pattern matches, FOO is tried (and possibly further  items
5375         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
5376         skips  to  the second alternative and tries COND2, without backtracking         skips to the second alternative and tries COND2,  without  backtracking
5377         into COND1. If (*THEN) is used outside  of  any  alternation,  it  acts         into  COND1.  The  behaviour  of  (*THEN:NAME)  is  exactly the same as
5378         exactly like (*PRUNE).         (*MARK:NAME)(*THEN) if the overall  match  fails.  If  (*THEN)  is  not
5379           directly inside an alternation, it acts like (*PRUNE).
5380    
5381    
5382  SEE ALSO  SEE ALSO
# Line 5260  AUTHOR Line 5393  AUTHOR
5393    
5394  REVISION  REVISION
5395    
5396         Last updated: 06 March 2010         Last updated: 27 March 2010
5397         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
5398  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
5399    

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