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revision 1361 by ph10, Fri Sep 6 17:47:32 2013 UTC revision 1405 by ph10, Mon Nov 25 15:09:21 2013 UTC
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1  .TH PCREPATTERN 3 "06 September 2013" "PCRE 8.34"  .TH PCREPATTERN 3 "25 November 2013" "PCRE 8.34"
2  .SH NAME  .SH NAME
3  PCRE - Perl-compatible regular expressions  PCRE - Perl-compatible regular expressions
4  .SH "PCRE REGULAR EXPRESSION DETAILS"  .SH "PCRE REGULAR EXPRESSION DETAILS"
# Line 80  appearance causes an error. Line 80  appearance causes an error.
80  .SS "Unicode property support"  .SS "Unicode property support"
81  .rs  .rs
82  .sp  .sp
83  Another special sequence that may appear at the start of a pattern is  Another special sequence that may appear at the start of a pattern is (*UCP).
 .sp  
   (*UCP)  
 .sp  
84  This has the same effect as setting the PCRE_UCP option: it causes sequences  This has the same effect as setting the PCRE_UCP option: it causes sequences
85  such as \ed and \ew to use Unicode properties to determine character types,  such as \ed and \ew to use Unicode properties to determine character types,
86  instead of recognizing only characters with codes less than 128 via a lookup  instead of recognizing only characters with codes less than 128 via a lookup
87  table.  table.
88  .  .
89  .  .
90    .SS "Disabling auto-possessification"
91    .rs
92    .sp
93    If a pattern starts with (*NO_AUTO_POSSESS), it has the same effect as setting
94    the PCRE_NO_AUTO_POSSESS option at compile time. This stops PCRE from making
95    quantifiers possessive when what follows cannot match the repeated item. For
96    example, by default a+b is treated as a++b. For more details, see the
97    .\" HREF
98    \fBpcreapi\fP
99    .\"
100    documentation.
101    .
102    .
103  .SS "Disabling start-up optimizations"  .SS "Disabling start-up optimizations"
104  .rs  .rs
105  .sp  .sp
106  If a pattern starts with (*NO_START_OPT), it has the same effect as setting the  If a pattern starts with (*NO_START_OPT), it has the same effect as setting the
107  PCRE_NO_START_OPTIMIZE option either at compile or matching time.  PCRE_NO_START_OPTIMIZE option either at compile or matching time. This disables
108    several optimizations for quickly reaching "no match" results. For more
109    details, see the
110    .\" HREF
111    \fBpcreapi\fP
112    .\"
113    documentation.
114  .  .
115  .  .
116  .\" HTML <a name="newlines"></a>  .\" HTML <a name="newlines"></a>
# Line 164  pattern of the form Line 180  pattern of the form
180    (*LIMIT_RECURSION=d)    (*LIMIT_RECURSION=d)
181  .sp  .sp
182  where d is any number of decimal digits. However, the value of the setting must  where d is any number of decimal digits. However, the value of the setting must
183  be less than the value set by the caller of \fBpcre_exec()\fP for it to have  be less than the value set (or defaulted) by the caller of \fBpcre_exec()\fP
184  any effect. In other words, the pattern writer can lower the limit set by the  for it to have any effect. In other words, the pattern writer can lower the
185  programmer, but not raise it. If there is more than one setting of one of these  limits set by the programmer, but not raise them. If there is more than one
186  limits, the lower value is used.  setting of one of these limits, the lower value is used.
187  .  .
188  .  .
189  .SH "EBCDIC CHARACTER CODES"  .SH "EBCDIC CHARACTER CODES"
# Line 257  In a UTF mode, only ASCII numbers and le Line 273  In a UTF mode, only ASCII numbers and le
273  backslash. All other characters (in particular, those whose codepoints are  backslash. All other characters (in particular, those whose codepoints are
274  greater than 127) are treated as literals.  greater than 127) are treated as literals.
275  .P  .P
276  If a pattern is compiled with the PCRE_EXTENDED option, white space in the  If a pattern is compiled with the PCRE_EXTENDED option, most white space in the
277  pattern (other than in a character class) and characters between a # outside  pattern (other than in a character class), and characters between a # outside a
278  a character class and the next newline are ignored. An escaping backslash can  character class and the next newline, inclusive, are ignored. An escaping
279  be used to include a white space or # character as part of the pattern.  backslash can be used to include a white space or # character as part of the
280    pattern.
281  .P  .P
282  If you want to remove the special meaning from a sequence of characters, you  If you want to remove the special meaning from a sequence of characters, you
283  can do so by putting them between \eQ and \eE. This is different from Perl in  can do so by putting them between \eQ and \eE. This is different from Perl in
# Line 300  one of the following escape sequences th Line 317  one of the following escape sequences th
317    \en        linefeed (hex 0A)    \en        linefeed (hex 0A)
318    \er        carriage return (hex 0D)    \er        carriage return (hex 0D)
319    \et        tab (hex 09)    \et        tab (hex 09)
320      \e0dd      character with octal code 0dd
321    \eddd      character with octal code ddd, or back reference    \eddd      character with octal code ddd, or back reference
322      \eo{ddd..} character with octal code ddd..
323    \exhh      character with hex code hh    \exhh      character with hex code hh
324    \ex{hhh..} character with hex code hhh.. (non-JavaScript mode)    \ex{hhh..} character with hex code hhh.. (non-JavaScript mode)
325    \euhhhh    character with hex code hhhh (JavaScript mode only)    \euhhhh    character with hex code hhhh (JavaScript mode only)
# Line 321  byte are inverted. Thus \ecA becomes hex Line 340  byte are inverted. Thus \ecA becomes hex
340  the EBCDIC letters are disjoint, \ecZ becomes hex 29 (Z is E9), and other  the EBCDIC letters are disjoint, \ecZ becomes hex 29 (Z is E9), and other
341  characters also generate different values.  characters also generate different values.
342  .P  .P
 By default, after \ex, from zero to two hexadecimal digits are read (letters  
 can be in upper or lower case). Any number of hexadecimal digits may appear  
 between \ex{ and }, but the character code is constrained as follows:  
 .sp  
   8-bit non-UTF mode    less than 0x100  
   8-bit UTF-8 mode      less than 0x10ffff and a valid codepoint  
   16-bit non-UTF mode   less than 0x10000  
   16-bit UTF-16 mode    less than 0x10ffff and a valid codepoint  
   32-bit non-UTF mode   less than 0x80000000  
   32-bit UTF-32 mode    less than 0x10ffff and a valid codepoint  
 .sp  
 Invalid Unicode codepoints are the range 0xd800 to 0xdfff (the so-called  
 "surrogate" codepoints), and 0xffef.  
 .P  
 If characters other than hexadecimal digits appear between \ex{ and }, or if  
 there is no terminating }, this form of escape is not recognized. Instead, the  
 initial \ex will be interpreted as a basic hexadecimal escape, with no  
 following digits, giving a character whose value is zero.  
 .P  
 If the PCRE_JAVASCRIPT_COMPAT option is set, the interpretation of \ex is  
 as just described only when it is followed by two hexadecimal digits.  
 Otherwise, it matches a literal "x" character. In JavaScript mode, support for  
 code points greater than 256 is provided by \eu, which must be followed by  
 four hexadecimal digits; otherwise it matches a literal "u" character.  
 Character codes specified by \eu in JavaScript mode are constrained in the same  
 was as those specified by \ex in non-JavaScript mode.  
 .P  
 Characters whose value is less than 256 can be defined by either of the two  
 syntaxes for \ex (or by \eu in JavaScript mode). There is no difference in the  
 way they are handled. For example, \exdc is exactly the same as \ex{dc} (or  
 \eu00dc in JavaScript mode).  
 .P  
343  After \e0 up to two further octal digits are read. If there are fewer than two  After \e0 up to two further octal digits are read. If there are fewer than two
344  digits, just those that are present are used. Thus the sequence \e0\ex\e07  digits, just those that are present are used. Thus the sequence \e0\ex\e07
345  specifies two binary zeros followed by a BEL character (code value 7). Make  specifies two binary zeros followed by a BEL character (code value 7). Make
346  sure you supply two digits after the initial zero if the pattern character that  sure you supply two digits after the initial zero if the pattern character that
347  follows is itself an octal digit.  follows is itself an octal digit.
348  .P  .P
349  The handling of a backslash followed by a digit other than 0 is complicated.  The escape \eo must be followed by a sequence of octal digits, enclosed in
350  Outside a character class, PCRE reads it and any following digits as a decimal  braces. An error occurs if this is not the case. This escape is a recent
351  number. If the number is less than 10, or if there have been at least that many  addition to Perl; it provides way of specifying character code points as octal
352    numbers greater than 0777, and it also allows octal numbers and back references
353    to be unambiguously specified.
354    .P
355    For greater clarity and unambiguity, it is best to avoid following \e by a
356    digit greater than zero. Instead, use \eo{} or \ex{} to specify character
357    numbers, and \eg{} to specify back references. The following paragraphs
358    describe the old, ambiguous syntax.
359    .P
360    The handling of a backslash followed by a digit other than 0 is complicated,
361    and Perl has changed in recent releases, causing PCRE also to change. Outside a
362    character class, PCRE reads the digit and any following digits as a decimal
363    number. If the number is less than 8, or if there have been at least that many
364  previous capturing left parentheses in the expression, the entire sequence is  previous capturing left parentheses in the expression, the entire sequence is
365  taken as a \fIback reference\fP. A description of how this works is given  taken as a \fIback reference\fP. A description of how this works is given
366  .\" HTML <a href="#backreferences">  .\" HTML <a href="#backreferences">
# Line 374  following the discussion of Line 373  following the discussion of
373  parenthesized subpatterns.  parenthesized subpatterns.
374  .\"  .\"
375  .P  .P
376  Inside a character class, or if the decimal number is greater than 9 and there  Inside a character class, or if the decimal number following \e is greater than
377  have not been that many capturing subpatterns, PCRE re-reads up to three octal  7 and there have not been that many capturing subpatterns, PCRE handles \e8 and
378  digits following the backslash, and uses them to generate a data character. Any  \e9 as the literal characters "8" and "9", and otherwise re-reads up to three
379  subsequent digits stand for themselves. The value of the character is  octal digits following the backslash, using them to generate a data character.
380  constrained in the same way as characters specified in hexadecimal.  Any subsequent digits stand for themselves. For example:
 For example:  
381  .sp  .sp
382    \e040   is another way of writing an ASCII space    \e040   is another way of writing an ASCII space
383  .\" JOIN  .\" JOIN
# Line 398  For example: Line 396  For example:
396    \e377   might be a back reference, otherwise    \e377   might be a back reference, otherwise
397              the value 255 (decimal)              the value 255 (decimal)
398  .\" JOIN  .\" JOIN
399    \e81    is either a back reference, or a binary zero    \e81    is either a back reference, or the two
400              followed by the two characters "8" and "1"              characters "8" and "1"
401  .sp  .sp
402  Note that octal values of 100 or greater must not be introduced by a leading  Note that octal values of 100 or greater that are specified using this syntax
403  zero, because no more than three octal digits are ever read.  must not be introduced by a leading zero, because no more than three octal
404    digits are ever read.
405    .P
406    By default, after \ex that is not followed by {, from zero to two hexadecimal
407    digits are read (letters can be in upper or lower case). Any number of
408    hexadecimal digits may appear between \ex{ and }. If a character other than
409    a hexadecimal digit appears between \ex{ and }, or if there is no terminating
410    }, an error occurs.
411    .P
412    If the PCRE_JAVASCRIPT_COMPAT option is set, the interpretation of \ex is
413    as just described only when it is followed by two hexadecimal digits.
414    Otherwise, it matches a literal "x" character. In JavaScript mode, support for
415    code points greater than 256 is provided by \eu, which must be followed by
416    four hexadecimal digits; otherwise it matches a literal "u" character.
417  .P  .P
418    Characters whose value is less than 256 can be defined by either of the two
419    syntaxes for \ex (or by \eu in JavaScript mode). There is no difference in the
420    way they are handled. For example, \exdc is exactly the same as \ex{dc} (or
421    \eu00dc in JavaScript mode).
422    .
423    .
424    .SS "Constraints on character values"
425    .rs
426    .sp
427    Characters that are specified using octal or hexadecimal numbers are
428    limited to certain values, as follows:
429    .sp
430      8-bit non-UTF mode    less than 0x100
431      8-bit UTF-8 mode      less than 0x10ffff and a valid codepoint
432      16-bit non-UTF mode   less than 0x10000
433      16-bit UTF-16 mode    less than 0x10ffff and a valid codepoint
434      32-bit non-UTF mode   less than 0x100000000
435      32-bit UTF-32 mode    less than 0x10ffff and a valid codepoint
436    .sp
437    Invalid Unicode codepoints are the range 0xd800 to 0xdfff (the so-called
438    "surrogate" codepoints), and 0xffef.
439    .
440    .
441    .SS "Escape sequences in character classes"
442    .rs
443    .sp
444  All the sequences that define a single character value can be used both inside  All the sequences that define a single character value can be used both inside
445  and outside character classes. In addition, inside a character class, \eb is  and outside character classes. In addition, inside a character class, \eb is
446  interpreted as the backspace character (hex 08).  interpreted as the backspace character (hex 08).
# Line 494  classes. They each match one character o Line 531  classes. They each match one character o
531  matching point is at the end of the subject string, all of them fail, because  matching point is at the end of the subject string, all of them fail, because
532  there is no character to match.  there is no character to match.
533  .P  .P
534  For compatibility with Perl, \es does not match the VT character (code 11).  For compatibility with Perl, \es did not used to match the VT character (code
535  This makes it different from the the POSIX "space" class. The \es characters  11), which made it different from the the POSIX "space" class. However, Perl
536  are HT (9), LF (10), FF (12), CR (13), and space (32). If "use locale;" is  added VT at release 5.18, and PCRE followed suit at release 8.34. The default
537  included in a Perl script, \es may match the VT character. In PCRE, it never  \es characters are now HT (9), LF (10), VT (11), FF (12), CR (13), and space
538  does.  (32), which are defined as white space in the "C" locale. This list may vary if
539    locale-specific matching is taking place. For example, in some locales the
540    "non-breaking space" character (\exA0) is recognized as white space, and in
541    others the VT character is not.
542  .P  .P
543  A "word" character is an underscore or any character that is a letter or digit.  A "word" character is an underscore or any character that is a letter or digit.
544  By default, the definition of letters and digits is controlled by PCRE's  By default, the definition of letters and digits is controlled by PCRE's
# Line 513  in the Line 553  in the
553  \fBpcreapi\fP  \fBpcreapi\fP
554  .\"  .\"
555  page). For example, in a French locale such as "fr_FR" in Unix-like systems,  page). For example, in a French locale such as "fr_FR" in Unix-like systems,
556  or "french" in Windows, some character codes greater than 128 are used for  or "french" in Windows, some character codes greater than 127 are used for
557  accented letters, and these are then matched by \ew. The use of locales with  accented letters, and these are then matched by \ew. The use of locales with
558  Unicode is discouraged.  Unicode is discouraged.
559  .P  .P
560  By default, in a UTF mode, characters with values greater than 128 never match  By default, characters whose code points are greater than 127 never match \ed,
561  \ed, \es, or \ew, and always match \eD, \eS, and \eW. These sequences retain  \es, or \ew, and always match \eD, \eS, and \eW, although this may vary for
562  their original meanings from before UTF support was available, mainly for  characters in the range 128-255 when locale-specific matching is happening.
563  efficiency reasons. However, if PCRE is compiled with Unicode property support,  These escape sequences retain their original meanings from before Unicode
564  and the PCRE_UCP option is set, the behaviour is changed so that Unicode  support was available, mainly for efficiency reasons. If PCRE is compiled with
565  properties are used to determine character types, as follows:  Unicode property support, and the PCRE_UCP option is set, the behaviour is
566  .sp  changed so that Unicode properties are used to determine character types, as
567    \ed  any character that \ep{Nd} matches (decimal digit)  follows:
568    \es  any character that \ep{Z} matches, plus HT, LF, FF, CR  .sp
569    \ew  any character that \ep{L} or \ep{N} matches, plus underscore    \ed  any character that matches \ep{Nd} (decimal digit)
570      \es  any character that matches \ep{Z} or \eh or \ev
571      \ew  any character that matches \ep{L} or \ep{N}, plus underscore
572  .sp  .sp
573  The upper case escapes match the inverse sets of characters. Note that \ed  The upper case escapes match the inverse sets of characters. Note that \ed
574  matches only decimal digits, whereas \ew matches any Unicode digit, as well as  matches only decimal digits, whereas \ew matches any Unicode digit, as well as
# Line 536  is noticeably slower when PCRE_UCP is se Line 578  is noticeably slower when PCRE_UCP is se
578  .P  .P
579  The sequences \eh, \eH, \ev, and \eV are features that were added to Perl at  The sequences \eh, \eH, \ev, and \eV are features that were added to Perl at
580  release 5.10. In contrast to the other sequences, which match only ASCII  release 5.10. In contrast to the other sequences, which match only ASCII
581  characters by default, these always match certain high-valued codepoints,  characters by default, these always match certain high-valued code points,
582  whether or not PCRE_UCP is set. The horizontal space characters are:  whether or not PCRE_UCP is set. The horizontal space characters are:
583  .sp  .sp
584    U+0009     Horizontal tab (HT)    U+0009     Horizontal tab (HT)
# Line 906  the "mark" property always have the "ext Line 948  the "mark" property always have the "ext
948  .sp  .sp
949  As well as the standard Unicode properties described above, PCRE supports four  As well as the standard Unicode properties described above, PCRE supports four
950  more that make it possible to convert traditional escape sequences such as \ew  more that make it possible to convert traditional escape sequences such as \ew
951  and \es and POSIX character classes to use Unicode properties. PCRE uses these  and \es to use Unicode properties. PCRE uses these non-standard, non-Perl
952  non-standard, non-Perl properties internally when PCRE_UCP is set. However,  properties internally when PCRE_UCP is set. However, they may also be used
953  they may also be used explicitly. These properties are:  explicitly. These properties are:
954  .sp  .sp
955    Xan   Any alphanumeric character    Xan   Any alphanumeric character
956    Xps   Any POSIX space character    Xps   Any POSIX space character
# Line 918  they may also be used explicitly. These Line 960  they may also be used explicitly. These
960  Xan matches characters that have either the L (letter) or the N (number)  Xan matches characters that have either the L (letter) or the N (number)
961  property. Xps matches the characters tab, linefeed, vertical tab, form feed, or  property. Xps matches the characters tab, linefeed, vertical tab, form feed, or
962  carriage return, and any other character that has the Z (separator) property.  carriage return, and any other character that has the Z (separator) property.
963  Xsp is the same as Xps, except that vertical tab is excluded. Xwd matches the  Xsp is the same as Xps; it used to exclude vertical tab, for Perl
964  same characters as Xan, plus underscore.  compatibility, but Perl changed, and so PCRE followed at release 8.34. Xwd
965    matches the same characters as Xan, plus underscore.
966  .P  .P
967  There is another non-standard property, Xuc, which matches any character that  There is another non-standard property, Xuc, which matches any character that
968  can be represented by a Universal Character Name in C++ and other programming  can be represented by a Universal Character Name in C++ and other programming
# Line 1215  The minus (hyphen) character can be used Line 1258  The minus (hyphen) character can be used
1258  character class. For example, [d-m] matches any letter between d and m,  character class. For example, [d-m] matches any letter between d and m,
1259  inclusive. If a minus character is required in a class, it must be escaped with  inclusive. If a minus character is required in a class, it must be escaped with
1260  a backslash or appear in a position where it cannot be interpreted as  a backslash or appear in a position where it cannot be interpreted as
1261  indicating a range, typically as the first or last character in the class.  indicating a range, typically as the first or last character in the class, or
1262    immediately after a range. For example, [b-d-z] matches letters in the range b
1263    to d, a hyphen character, or z.
1264  .P  .P
1265  It is not possible to have the literal character "]" as the end character of a  It is not possible to have the literal character "]" as the end character of a
1266  range. A pattern such as [W-]46] is interpreted as a class of two characters  range. A pattern such as [W-]46] is interpreted as a class of two characters
# Line 1225  the end of range, so [W-\e]46] is interp Line 1270  the end of range, so [W-\e]46] is interp
1270  followed by two other characters. The octal or hexadecimal representation of  followed by two other characters. The octal or hexadecimal representation of
1271  "]" can also be used to end a range.  "]" can also be used to end a range.
1272  .P  .P
1273    An error is generated if a POSIX character class (see below) or an escape
1274    sequence other than one that defines a single character appears at a point
1275    where a range ending character is expected. For example, [z-\exff] is valid,
1276    but [A-\ed] and [A-[:digit:]] are not.
1277    .P
1278  Ranges operate in the collating sequence of character values. They can also be  Ranges operate in the collating sequence of character values. They can also be
1279  used for characters specified numerically, for example [\e000-\e037]. Ranges  used for characters specified numerically, for example [\e000-\e037]. Ranges
1280  can include any characters that are valid for the current mode.  can include any characters that are valid for the current mode.
# Line 1290  are: Line 1340  are:
1340    lower    lower case letters    lower    lower case letters
1341    print    printing characters, including space    print    printing characters, including space
1342    punct    printing characters, excluding letters and digits and space    punct    printing characters, excluding letters and digits and space
1343    space    white space (not quite the same as \es)    space    white space (the same as \es from PCRE 8.34)
1344    upper    upper case letters    upper    upper case letters
1345    word     "word" characters (same as \ew)    word     "word" characters (same as \ew)
1346    xdigit   hexadecimal digits    xdigit   hexadecimal digits
1347  .sp  .sp
1348  The "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13), and  The default "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),
1349  space (32). Notice that this list includes the VT character (code 11). This  and space (32). If locale-specific matching is taking place, the list of space
1350  makes "space" different to \es, which does not include VT (for Perl  characters may be different; there may be fewer or more of them. "Space" used
1351  compatibility).  to be different to \es, which did not include VT, for Perl compatibility.
1352    However, Perl changed at release 5.18, and PCRE followed at release 8.34.
1353    "Space" and \es now match the same set of characters.
1354  .P  .P
1355  The name "word" is a Perl extension, and "blank" is a GNU extension from Perl  The name "word" is a Perl extension, and "blank" is a GNU extension from Perl
1356  5.8. Another Perl extension is negation, which is indicated by a ^ character  5.8. Another Perl extension is negation, which is indicated by a ^ character
# Line 1310  matches "1", "2", or any non-digit. PCRE Line 1362  matches "1", "2", or any non-digit. PCRE
1362  syntax [.ch.] and [=ch=] where "ch" is a "collating element", but these are not  syntax [.ch.] and [=ch=] where "ch" is a "collating element", but these are not
1363  supported, and an error is given if they are encountered.  supported, and an error is given if they are encountered.
1364  .P  .P
1365  By default, in UTF modes, characters with values greater than 128 do not match  By default, characters with values greater than 128 do not match any of the
1366  any of the POSIX character classes. However, if the PCRE_UCP option is passed  POSIX character classes. However, if the PCRE_UCP option is passed to
1367  to \fBpcre_compile()\fP, some of the classes are changed so that Unicode  \fBpcre_compile()\fP, some of the classes are changed so that Unicode character
1368  character properties are used. This is achieved by replacing the POSIX classes  properties are used. This is achieved by replacing certain POSIX classes by
1369  by other sequences, as follows:  other sequences, as follows:
1370  .sp  .sp
1371    [:alnum:]  becomes  \ep{Xan}    [:alnum:]  becomes  \ep{Xan}
1372    [:alpha:]  becomes  \ep{L}    [:alpha:]  becomes  \ep{L}
# Line 1325  by other sequences, as follows: Line 1377  by other sequences, as follows:
1377    [:upper:]  becomes  \ep{Lu}    [:upper:]  becomes  \ep{Lu}
1378    [:word:]   becomes  \ep{Xwd}    [:word:]   becomes  \ep{Xwd}
1379  .sp  .sp
1380  Negated versions, such as [:^alpha:] use \eP instead of \ep. The other POSIX  Negated versions, such as [:^alpha:] use \eP instead of \ep. Three other POSIX
1381  classes are unchanged, and match only characters with code points less than  classes are handled specially in UCP mode:
1382  128.  .TP 10
1383    [:graph:]
1384    This matches characters that have glyphs that mark the page when printed. In
1385    Unicode property terms, it matches all characters with the L, M, N, P, S, or Cf
1386    properties, except for:
1387    .sp
1388      U+061C           Arabic Letter Mark
1389      U+180E           Mongolian Vowel Separator
1390      U+2066 - U+2069  Various "isolate"s
1391    .sp
1392    .TP 10
1393    [:print:]
1394    This matches the same characters as [:graph:] plus space characters that are
1395    not controls, that is, characters with the Zs property.
1396    .TP 10
1397    [:punct:]
1398    This matches all characters that have the Unicode P (punctuation) property,
1399    plus those characters whose code points are less than 128 that have the S
1400    (Symbol) property.
1401    .P
1402    The other POSIX classes are unchanged, and match only characters with code
1403    points less than 128.
1404  .  .
1405  .  .
1406  .SH "VERTICAL BAR"  .SH "VERTICAL BAR"
# Line 1547  conditions, Line 1620  conditions,
1620  .\"  .\"
1621  can be made by name as well as by number.  can be made by name as well as by number.
1622  .P  .P
1623  Names consist of up to 32 alphanumeric characters and underscores. Named  Names consist of up to 32 alphanumeric characters and underscores, but must
1624  capturing parentheses are still allocated numbers as well as names, exactly as  start with a non-digit. Named capturing parentheses are still allocated numbers
1625  if the names were not present. The PCRE API provides function calls for  as well as names, exactly as if the names were not present. The PCRE API
1626  extracting the name-to-number translation table from a compiled pattern. There  provides function calls for extracting the name-to-number translation table
1627  is also a convenience function for extracting a captured substring by name.  from a compiled pattern. There is also a convenience function for extracting a
1628    captured substring by name.
1629  .P  .P
1630  By default, a name must be unique within a pattern, but it is possible to relax  By default, a name must be unique within a pattern, but it is possible to relax
1631  this constraint by setting the PCRE_DUPNAMES option at compile time. (Duplicate  this constraint by setting the PCRE_DUPNAMES option at compile time. (Duplicate
# Line 1577  for the first (and in this example, the Line 1651  for the first (and in this example, the
1651  matched. This saves searching to find which numbered subpattern it was.  matched. This saves searching to find which numbered subpattern it was.
1652  .P  .P
1653  If you make a back reference to a non-unique named subpattern from elsewhere in  If you make a back reference to a non-unique named subpattern from elsewhere in
1654  the pattern, the subpatterns to which the name refers are checked in the order  the pattern, the subpatterns to which the name refers are checked in the order
1655  in which they appear in the overall pattern. The first one that is set is used  in which they appear in the overall pattern. The first one that is set is used
1656  for the reference. For example, this pattern matches both "foofoo" and  for the reference. For example, this pattern matches both "foofoo" and
1657  "barbar" but not "foobar" or "barfoo":  "barbar" but not "foobar" or "barfoo":
1658  .sp  .sp
1659    (?:(?<n>foo)|(?<n>bar))\k<n>    (?:(?<n>foo)|(?<n>bar))\ek<n>
1660  .sp  .sp
1661  .P  .P
1662  If you make a subroutine call to a non-unique named subpattern, the one that  If you make a subroutine call to a non-unique named subpattern, the one that
# Line 2283  This makes the fragment independent of t Line 2357  This makes the fragment independent of t
2357  .sp  .sp
2358  Perl uses the syntax (?(<name>)...) or (?('name')...) to test for a used  Perl uses the syntax (?(<name>)...) or (?('name')...) to test for a used
2359  subpattern by name. For compatibility with earlier versions of PCRE, which had  subpattern by name. For compatibility with earlier versions of PCRE, which had
2360  this facility before Perl, the syntax (?(name)...) is also recognized. However,  this facility before Perl, the syntax (?(name)...) is also recognized.
 there is a possible ambiguity with this syntax, because subpattern names may  
 consist entirely of digits. PCRE looks first for a named subpattern; if it  
 cannot find one and the name consists entirely of digits, PCRE looks for a  
 subpattern of that number, which must be greater than zero. Using subpattern  
 names that consist entirely of digits is not recommended.  
2361  .P  .P
2362  Rewriting the above example to use a named subpattern gives this:  Rewriting the above example to use a named subpattern gives this:
2363  .sp  .sp
# Line 2710  During matching, when PCRE reaches a cal Line 2779  During matching, when PCRE reaches a cal
2779  called. It is provided with the number of the callout, the position in the  called. It is provided with the number of the callout, the position in the
2780  pattern, and, optionally, one item of data originally supplied by the caller of  pattern, and, optionally, one item of data originally supplied by the caller of
2781  the matching function. The callout function may cause matching to proceed, to  the matching function. The callout function may cause matching to proceed, to
2782  backtrack, or to fail altogether. A complete description of the interface to  backtrack, or to fail altogether.
2783  the callout function is given in the  .P
2784    By default, PCRE implements a number of optimizations at compile time and
2785    matching time, and one side-effect is that sometimes callouts are skipped. If
2786    you need all possible callouts to happen, you need to set options that disable
2787    the relevant optimizations. More details, and a complete description of the
2788    interface to the callout function, are given in the
2789  .\" HREF  .\" HREF
2790  \fBpcrecallout\fP  \fBpcrecallout\fP
2791  .\"  .\"
# Line 3157  Cambridge CB2 3QH, England. Line 3231  Cambridge CB2 3QH, England.
3231  .rs  .rs
3232  .sp  .sp
3233  .nf  .nf
3234  Last updated: 06 September 2013  Last updated: 25 November 2013
3235  Copyright (c) 1997-2013 University of Cambridge.  Copyright (c) 1997-2013 University of Cambridge.
3236  .fi  .fi

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