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revision 575 by ph10, Sun Nov 21 12:55:42 2010 UTC revision 579 by ph10, Wed Nov 24 17:39:25 2010 UTC
# Line 52  such as \ed and \ew to use Unicode prope Line 52  such as \ed and \ew to use Unicode prope
52  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
53  table.  table.
54  .P  .P
55    If a pattern starts with (*NO_START_OPT), it has the same effect as setting the
56    PCRE_NO_START_OPTIMIZE option either at compile or matching time. There are
57    also some more of these special sequences that are concerned with the handling
58    of newlines; they are described below.
59    .P
60  The remainder of this document discusses the patterns that are supported by  The remainder of this document discusses the patterns that are supported by
61  PCRE when its main matching function, \fBpcre_exec()\fP, is used.  PCRE when its main matching function, \fBpcre_exec()\fP, is used.
62  From release 6.0, PCRE offers a second matching function,  From release 6.0, PCRE offers a second matching function,
# Line 184  The following sections describe the use Line 189  The following sections describe the use
189  The backslash character has several uses. Firstly, if it is followed by a  The backslash character has several uses. Firstly, if it is followed by a
190  character that is not a number or a letter, it takes away any special meaning  character that is not a number or a letter, it takes away any special meaning
191  that character may have. This use of backslash as an escape character applies  that character may have. This use of backslash as an escape character applies
192  both inside and outside character classes.  both inside and outside character classes.
193  .P  .P
194  For example, if you want to match a * character, you write \e* in the pattern.  For example, if you want to match a * character, you write \e* in the pattern.
195  This escaping action applies whether or not the following character would  This escaping action applies whether or not the following character would
# Line 193  non-alphanumeric with backslash to speci Line 198  non-alphanumeric with backslash to speci
198  particular, if you want to match a backslash, you write \e\e.  particular, if you want to match a backslash, you write \e\e.
199  .P  .P
200  In UTF-8 mode, only ASCII numbers and letters have any special meaning after a  In UTF-8 mode, only ASCII numbers and letters have any special meaning after a
201  backslash. All other characters (in particular, those whose codepoints are  backslash. All other characters (in particular, those whose codepoints are
202  greater than 127) are treated as literals.  greater than 127) are treated as literals.
203  .P  .P
204  If a pattern is compiled with the PCRE_EXTENDED option, whitespace in the  If a pattern is compiled with the PCRE_EXTENDED option, whitespace in the
# Line 242  one of the following escape sequences th Line 247  one of the following escape sequences th
247  The precise effect of \ecx is as follows: if x is a lower case letter, it  The precise effect of \ecx is as follows: if x is a lower case letter, it
248  is converted to upper case. Then bit 6 of the character (hex 40) is inverted.  is converted to upper case. Then bit 6 of the character (hex 40) is inverted.
249  Thus \ecz becomes hex 1A (z is 7A), but \ec{ becomes hex 3B ({ is 7B), while  Thus \ecz becomes hex 1A (z is 7A), but \ec{ becomes hex 3B ({ is 7B), while
250  \ec; becomes hex 7B (; is 3B). If the byte following \ec has a value greater  \ec; becomes hex 7B (; is 3B). If the byte following \ec has a value greater
251  than 127, a compile-time error occurs. This locks out non-ASCII characters in  than 127, a compile-time error occurs. This locks out non-ASCII characters in
252  both byte mode and UTF-8 mode. (When PCRE is compiled in EBCDIC mode, all byte  both byte mode and UTF-8 mode. (When PCRE is compiled in EBCDIC mode, all byte
253  values are valid. A lower case letter is converted to upper case, and then the  values are valid. A lower case letter is converted to upper case, and then the
254  0xc0 bits are flipped.)  0xc0 bits are flipped.)
255  .P  .P
256  After \ex, from zero to two hexadecimal digits are read (letters can be in  After \ex, from zero to two hexadecimal digits are read (letters can be in
# Line 432  any Unicode letter, and underscore. Note Line 437  any Unicode letter, and underscore. Note
437  \eB because they are defined in terms of \ew and \eW. Matching these sequences  \eB because they are defined in terms of \ew and \eW. Matching these sequences
438  is noticeably slower when PCRE_UCP is set.  is noticeably slower when PCRE_UCP is set.
439  .P  .P
440  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
441  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
442  characters by default, these always match certain high-valued codepoints in  characters by default, these always match certain high-valued codepoints in
443  UTF-8 mode, whether or not PCRE_UCP is set. The horizontal space characters  UTF-8 mode, whether or not PCRE_UCP is set. The horizontal space characters
# Line 955  The handling of dot is entirely independ Line 960  The handling of dot is entirely independ
960  dollar, the only relationship being that they both involve newlines. Dot has no  dollar, the only relationship being that they both involve newlines. Dot has no
961  special meaning in a character class.  special meaning in a character class.
962  .P  .P
963  The escape sequence \eN behaves like a dot, except that it is not affected by  The escape sequence \eN behaves like a dot, except that it is not affected by
964  the PCRE_DOTALL option. In other words, it matches any character except one  the PCRE_DOTALL option. In other words, it matches any character except one
965  that signifies the end of a line.  that signifies the end of a line.
966  .  .
# Line 1071  default, but cause an error if the PCRE_ Line 1076  default, but cause an error if the PCRE_
1076  A circumflex can conveniently be used with the upper case character types to  A circumflex can conveniently be used with the upper case character types to
1077  specify a more restricted set of characters than the matching lower case type.  specify a more restricted set of characters than the matching lower case type.
1078  For example, the class [^\eW_] matches any letter or digit, but not underscore,  For example, the class [^\eW_] matches any letter or digit, but not underscore,
1079  whereas [\ew] includes underscore. A positive character class should be read as  whereas [\ew] includes underscore. A positive character class should be read as
1080  "something OR something OR ..." and a negative class as "NOT something AND NOT  "something OR something OR ..." and a negative class as "NOT something AND NOT
1081  something AND NOT ...".  something AND NOT ...".
1082  .P  .P
1083  The only metacharacters that are recognized in character classes are backslash,  The only metacharacters that are recognized in character classes are backslash,
# Line 1992  already been matched. The two possible f Line 1997  already been matched. The two possible f
1997  If the condition is satisfied, the yes-pattern is used; otherwise the  If the condition is satisfied, the yes-pattern is used; otherwise the
1998  no-pattern (if present) is used. If there are more than two alternatives in the  no-pattern (if present) is used. If there are more than two alternatives in the
1999  subpattern, a compile-time error occurs. Each of the two alternatives may  subpattern, a compile-time error occurs. Each of the two alternatives may
2000  itself contain nested subpatterns of any form, including conditional  itself contain nested subpatterns of any form, including conditional
2001  subpatterns; the restriction to two alternatives applies only at the level of  subpatterns; the restriction to two alternatives applies only at the level of
2002  the condition. This pattern fragment is an example where the alternatives are  the condition. This pattern fragment is an example where the alternatives are
2003  complex:  complex:
2004  .sp  .sp
2005    (?(1) (A|B|C) | (D | (?(2)E|F) | E) )    (?(1) (A|B|C) | (D | (?(2)E|F) | E) )
# Line 2019  the condition is true if any of them hav Line 2024  the condition is true if any of them hav
2024  to precede the digits with a plus or minus sign. In this case, the subpattern  to precede the digits with a plus or minus sign. In this case, the subpattern
2025  number is relative rather than absolute. The most recently opened parentheses  number is relative rather than absolute. The most recently opened parentheses
2026  can be referenced by (?(-1), the next most recent by (?(-2), and so on. Inside  can be referenced by (?(-1), the next most recent by (?(-2), and so on. Inside
2027  loops it can also make sense to refer to subsequent groups. The next  loops it can also make sense to refer to subsequent groups. The next
2028  parentheses to be opened can be referenced as (?(+1), and so on. (The value  parentheses to be opened can be referenced as (?(+1), and so on. (The value
2029  zero in any of these forms is not used; it provokes a compile-time error.)  zero in any of these forms is not used; it provokes a compile-time error.)
2030  .P  .P
# Line 2139  dd-aaa-dd or dd-dd-dd, where aaa are let Line 2144  dd-aaa-dd or dd-dd-dd, where aaa are let
2144  .SH COMMENTS  .SH COMMENTS
2145  .rs  .rs
2146  .sp  .sp
2147  There are two ways of including comments in patterns that are processed by  There are two ways of including comments in patterns that are processed by
2148  PCRE. In both cases, the start of the comment must not be in a character class,  PCRE. In both cases, the start of the comment must not be in a character class,
2149  nor in the middle of any other sequence of related characters such as (?: or a  nor in the middle of any other sequence of related characters such as (?: or a
2150  subpattern name or number. The characters that make up a comment play no part  subpattern name or number. The characters that make up a comment play no part
# Line 2163  default newline convention is in force: Line 2168  default newline convention is in force:
2168  .sp  .sp
2169    abc #comment \en still comment    abc #comment \en still comment
2170  .sp  .sp
2171  On encountering the # character, \fBpcre_compile()\fP skips along, looking for  On encountering the # character, \fBpcre_compile()\fP skips along, looking for
2172  a newline in the pattern. The sequence \en is still literal at this stage, so  a newline in the pattern. The sequence \en is still literal at this stage, so
2173  it does not terminate the comment. Only an actual character with the code value  it does not terminate the comment. Only an actual character with the code value
2174  0x0a (the default newline) does so.  0x0a (the default newline) does so.
# Line 2497  minimum length of matching subject, or t Line 2502  minimum length of matching subject, or t
2502  present. When one of these optimizations suppresses the running of a match, any  present. When one of these optimizations suppresses the running of a match, any
2503  included backtracking verbs will not, of course, be processed. You can suppress  included backtracking verbs will not, of course, be processed. You can suppress
2504  the start-of-match optimizations by setting the PCRE_NO_START_OPTIMIZE option  the start-of-match optimizations by setting the PCRE_NO_START_OPTIMIZE option
2505  when calling \fBpcre_exec()\fP.  when calling \fBpcre_compile()\fP or \fBpcre_exec()\fP, or by starting the
2506    pattern with (*NO_START_OPT).
2507  .  .
2508  .  .
2509  .SS "Verbs that act immediately"  .SS "Verbs that act immediately"
# Line 2688  matching name is found, normal "bumpalon Line 2694  matching name is found, normal "bumpalon
2694  .sp  .sp
2695    (*THEN) or (*THEN:NAME)    (*THEN) or (*THEN:NAME)
2696  .sp  .sp
2697  This verb causes a skip to the next alternation in the innermost enclosing  This verb causes a skip to the next alternation in the innermost enclosing
2698  group if the rest of the pattern does not match. That is, it cancels pending  group if the rest of the pattern does not match. That is, it cancels pending
2699  backtracking, but only within the current alternation. Its name comes from the  backtracking, but only within the current alternation. Its name comes from the
2700  observation that it can be used for a pattern-based if-then-else block:  observation that it can be used for a pattern-based if-then-else block:
# Line 2703  overall match fails. If (*THEN) is not d Line 2709  overall match fails. If (*THEN) is not d
2709  like (*PRUNE).  like (*PRUNE).
2710  .  .
2711  .P  .P
2712  The above verbs provide four different "strengths" of control when subsequent  The above verbs provide four different "strengths" of control when subsequent
2713  matching fails. (*THEN) is the weakest, carrying on the match at the next  matching fails. (*THEN) is the weakest, carrying on the match at the next
2714  alternation. (*PRUNE) comes next, failing the match at the current starting  alternation. (*PRUNE) comes next, failing the match at the current starting
2715  position, but allowing an advance to the next character (for an unanchored  position, but allowing an advance to the next character (for an unanchored

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