-This file contains the PCRE man page that describes the regular expressions
-supported by PCRE version 5.0. Note that not all of the features are relevant
+This file contains the PCRE man page that describes the regular expressions
+supported by PCRE version 6.2. Note that not all of the features are relevant
in the context of Exim. In particular, the version of PCRE that is compiled
with Exim does not include UTF-8 support, there is no mechanism for changing
the options with which the PCRE functions are called, and features such as
callout are not accessible.
-----------------------------------------------------------------------------
-PCRE(3) PCRE(3)
-
+PCREPATTERN(3) PCREPATTERN(3)
NAME
PCRE - Perl-compatible regular expressions
+
PCRE REGULAR EXPRESSION DETAILS
The syntax and semantics of the regular expressions supported by PCRE
of UTF-8 features in the section on UTF-8 support in the main pcre
page.
+ The remainder of this document discusses the patterns that are sup-
+ ported by PCRE when its main matching function, pcre_exec(), is used.
+ From release 6.0, PCRE offers a second matching function,
+ pcre_dfa_exec(), which matches using a different algorithm that is not
+ Perl-compatible. The advantages and disadvantages of the alternative
+ function, and how it differs from the normal function, are discussed in
+ the pcrematching page.
+
A regular expression is a pattern that is matched against a subject
string from left to right. Most characters stand for themselves in a
pattern, and match the corresponding characters in the subject. As a
The quick brown fox
- matches a portion of a subject string that is identical to itself. The
- power of regular expressions comes from the ability to include alterna-
- tives and repetitions in the pattern. These are encoded in the pattern
- by the use of metacharacters, which do not stand for themselves but
- instead are interpreted in some special way.
-
- There are two different sets of metacharacters: those that are recog-
- nized anywhere in the pattern except within square brackets, and those
- that are recognized in square brackets. Outside square brackets, the
+ matches a portion of a subject string that is identical to itself. When
+ caseless matching is specified (the PCRE_CASELESS option), letters are
+ matched independently of case. In UTF-8 mode, PCRE always understands
+ the concept of case for characters whose values are less than 128, so
+ caseless matching is always possible. For characters with higher val-
+ ues, the concept of case is supported if PCRE is compiled with Unicode
+ property support, but not otherwise. If you want to use caseless
+ matching for characters 128 and above, you must ensure that PCRE is
+ compiled with Unicode property support as well as with UTF-8 support.
+
+ The power of regular expressions comes from the ability to include
+ alternatives and repetitions in the pattern. These are encoded in the
+ pattern by the use of metacharacters, which do not stand for themselves
+ but instead are interpreted in some special way.
+
+ There are two different sets of metacharacters: those that are recog-
+ nized anywhere in the pattern except within square brackets, and those
+ that are recognized in square brackets. Outside square brackets, the
metacharacters are as follows:
\ general escape character with several uses
also "possessive quantifier"
{ start min/max quantifier
- Part of a pattern that is in square brackets is called a "character
+ Part of a pattern that is in square brackets is called a "character
class". In a character class the only metacharacters are:
\ general escape character
syntax)
] terminates the character class
- The following sections describe the use of each of the metacharacters.
+ The following sections describe the use of each of the metacharacters.
BACKSLASH
The backslash character has several uses. Firstly, if it is followed by
- a non-alphanumeric character, it takes away any special meaning that
- character may have. This use of backslash as an escape character
+ a non-alphanumeric character, it takes away any special meaning that
+ character may have. This use of backslash as an escape character
applies both inside and outside character classes.
- For example, if you want to match a * character, you write \* in the
- pattern. This escaping action applies whether or not the following
- character would otherwise be interpreted as a metacharacter, so it is
- always safe to precede a non-alphanumeric with backslash to specify
- that it stands for itself. In particular, if you want to match a back-
+ For example, if you want to match a * character, you write \* in the
+ pattern. This escaping action applies whether or not the following
+ character would otherwise be interpreted as a metacharacter, so it is
+ always safe to precede a non-alphanumeric with backslash to specify
+ that it stands for itself. In particular, if you want to match a back-
slash, you write \\.
- If a pattern is compiled with the PCRE_EXTENDED option, whitespace in
- the pattern (other than in a character class) and characters between a
+ If a pattern is compiled with the PCRE_EXTENDED option, whitespace in
+ the pattern (other than in a character class) and characters between a
# outside a character class and the next newline character are ignored.
- An escaping backslash can be used to include a whitespace or # charac-
+ An escaping backslash can be used to include a whitespace or # charac-
ter as part of the pattern.
- If you want to remove the special meaning from a sequence of charac-
- ters, you can do so by putting them between \Q and \E. This is differ-
- ent from Perl in that $ and @ are handled as literals in \Q...\E
- sequences in PCRE, whereas in Perl, $ and @ cause variable interpola-
+ If you want to remove the special meaning from a sequence of charac-
+ ters, you can do so by putting them between \Q and \E. This is differ-
+ ent from Perl in that $ and @ are handled as literals in \Q...\E
+ sequences in PCRE, whereas in Perl, $ and @ cause variable interpola-
tion. Note the following examples:
Pattern PCRE matches Perl matches
\Qabc\$xyz\E abc\$xyz abc\$xyz
\Qabc\E\$\Qxyz\E abc$xyz abc$xyz
- The \Q...\E sequence is recognized both inside and outside character
+ The \Q...\E sequence is recognized both inside and outside character
classes.
Non-printing characters
A second use of backslash provides a way of encoding non-printing char-
- acters in patterns in a visible manner. There is no restriction on the
- appearance of non-printing characters, apart from the binary zero that
- terminates a pattern, but when a pattern is being prepared by text
- editing, it is usually easier to use one of the following escape
+ acters in patterns in a visible manner. There is no restriction on the
+ appearance of non-printing characters, apart from the binary zero that
+ terminates a pattern, but when a pattern is being prepared by text
+ editing, it is usually easier to use one of the following escape
sequences than the binary character it represents:
\a alarm, that is, the BEL character (hex 07)
\xhh character with hex code hh
\x{hhh..} character with hex code hhh... (UTF-8 mode only)
- The precise effect of \cx is as follows: if x is a lower case letter,
- it is converted to upper case. Then bit 6 of the character (hex 40) is
- inverted. Thus \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;
+ The precise effect of \cx is as follows: if x is a lower case letter,
+ it is converted to upper case. Then bit 6 of the character (hex 40) is
+ inverted. Thus \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;
becomes hex 7B.
- After \x, from zero to two hexadecimal digits are read (letters can be
- in upper or lower case). In UTF-8 mode, any number of hexadecimal dig-
- its may appear between \x{ and }, but the value of the character code
- must be less than 2**31 (that is, the maximum hexadecimal value is
- 7FFFFFFF). If characters other than hexadecimal digits appear between
- \x{ and }, or if there is no terminating }, this form of escape is not
- recognized. Instead, the initial \x will be interpreted as a basic hex-
- adecimal escape, with no following digits, giving a character whose
+ After \x, from zero to two hexadecimal digits are read (letters can be
+ in upper or lower case). In UTF-8 mode, any number of hexadecimal dig-
+ its may appear between \x{ and }, but the value of the character code
+ must be less than 2**31 (that is, the maximum hexadecimal value is
+ 7FFFFFFF). If characters other than hexadecimal digits appear between
+ \x{ and }, or if there is no terminating }, this form of escape is not
+ recognized. Instead, the initial \x will be interpreted as a basic
+ hexadecimal escape, with no following digits, giving a character whose
value is zero.
Characters whose value is less than 256 can be defined by either of the
- two syntaxes for \x when PCRE is in UTF-8 mode. There is no difference
- in the way they are handled. For example, \xdc is exactly the same as
+ two syntaxes for \x when PCRE is in UTF-8 mode. There is no difference
+ in the way they are handled. For example, \xdc is exactly the same as
\x{dc}.
- After \0 up to two further octal digits are read. In both cases, if
- there are fewer than two digits, just those that are present are used.
- Thus the sequence \0\x\07 specifies two binary zeros followed by a BEL
- character (code value 7). Make sure you supply two digits after the
- initial zero if the pattern character that follows is itself an octal
+ After \0 up to two further octal digits are read. In both cases, if
+ there are fewer than two digits, just those that are present are used.
+ Thus the sequence \0\x\07 specifies two binary zeros followed by a BEL
+ character (code value 7). Make sure you supply two digits after the
+ initial zero if the pattern character that follows is itself an octal
digit.
The handling of a backslash followed by a digit other than 0 is compli-
cated. Outside a character class, PCRE reads it and any following dig-
- its as a decimal number. If the number is less than 10, or if there
+ its as a decimal number. If the number is less than 10, or if there
have been at least that many previous capturing left parentheses in the
- expression, the entire sequence is taken as a back reference. A
- description of how this works is given later, following the discussion
+ expression, the entire sequence is taken as a back reference. A
+ description of how this works is given later, following the discussion
of parenthesized subpatterns.
- Inside a character class, or if the decimal number is greater than 9
- and there have not been that many capturing subpatterns, PCRE re-reads
- up to three octal digits following the backslash, and generates a sin-
+ Inside a character class, or if the decimal number is greater than 9
+ and there have not been that many capturing subpatterns, PCRE re-reads
+ up to three octal digits following the backslash, and generates a sin-
gle byte from the least significant 8 bits of the value. Any subsequent
digits stand for themselves. For example:
\81 is either a back reference, or a binary zero
followed by the two characters "8" and "1"
- Note that octal values of 100 or greater must not be introduced by a
+ Note that octal values of 100 or greater must not be introduced by a
leading zero, because no more than three octal digits are ever read.
- All the sequences that define a single byte value or a single UTF-8
+ All the sequences that define a single byte value or a single UTF-8
character (in UTF-8 mode) can be used both inside and outside character
- classes. In addition, inside a character class, the sequence \b is
+ classes. In addition, inside a character class, the sequence \b is
interpreted as the backspace character (hex 08), and the sequence \X is
- interpreted as the character "X". Outside a character class, these
+ interpreted as the character "X". Outside a character class, these
sequences have different meanings (see below).
Generic character types
- The third use of backslash is for specifying generic character types.
+ The third use of backslash is for specifying generic character types.
The following are always recognized:
\d any decimal digit
\W any "non-word" character
Each pair of escape sequences partitions the complete set of characters
- into two disjoint sets. Any given character matches one, and only one,
+ into two disjoint sets. Any given character matches one, and only one,
of each pair.
These character type sequences can appear both inside and outside char-
- acter classes. They each match one character of the appropriate type.
- If the current matching point is at the end of the subject string, all
+ acter classes. They each match one character of the appropriate type.
+ If the current matching point is at the end of the subject string, all
of them fail, since there is no character to match.
- For compatibility with Perl, \s does not match the VT character (code
- 11). This makes it different from the the POSIX "space" class. The \s
+ For compatibility with Perl, \s does not match the VT character (code
+ 11). This makes it different from the the POSIX "space" class. The \s
characters are HT (9), LF (10), FF (12), CR (13), and space (32).
A "word" character is an underscore or any character less than 256 that
- is a letter or digit. The definition of letters and digits is con-
- trolled by PCRE's low-valued character tables, and may vary if locale-
- specific matching is taking place (see "Locale support" in the pcreapi
- page). For example, in the "fr_FR" (French) locale, some character
- codes greater than 128 are used for accented letters, and these are
+ is a letter or digit. The definition of letters and digits is con-
+ trolled by PCRE's low-valued character tables, and may vary if locale-
+ specific matching is taking place (see "Locale support" in the pcreapi
+ page). For example, in the "fr_FR" (French) locale, some character
+ codes greater than 128 are used for accented letters, and these are
matched by \w.
- In UTF-8 mode, characters with values greater than 128 never match \d,
+ In UTF-8 mode, characters with values greater than 128 never match \d,
\s, or \w, and always match \D, \S, and \W. This is true even when Uni-
code character property support is available.
Unicode character properties
When PCRE is built with Unicode character property support, three addi-
- tional escape sequences to match generic character types are available
+ tional escape sequences to match generic character types are available
when UTF-8 mode is selected. They are:
\p{xx} a character with the xx property
\P{xx} a character without the xx property
\X an extended Unicode sequence
- The property names represented by xx above are limited to the Unicode
- general category properties. Each character has exactly one such prop-
- erty, specified by a two-letter abbreviation. For compatibility with
- Perl, negation can be specified by including a circumflex between the
- opening brace and the property name. For example, \p{^Lu} is the same
+ The property names represented by xx above are limited to the Unicode
+ general category properties. Each character has exactly one such prop-
+ erty, specified by a two-letter abbreviation. For compatibility with
+ Perl, negation can be specified by including a circumflex between the
+ opening brace and the property name. For example, \p{^Lu} is the same
as \P{Lu}.
- If only one letter is specified with \p or \P, it includes all the
+ If only one letter is specified with \p or \P, it includes all the
properties that start with that letter. In this case, in the absence of
negation, the curly brackets in the escape sequence are optional; these
two examples have the same effect:
Zp Paragraph separator
Zs Space separator
- Extended properties such as "Greek" or "InMusicalSymbols" are not sup-
+ Extended properties such as "Greek" or "InMusicalSymbols" are not sup-
ported by PCRE.
- Specifying caseless matching does not affect these escape sequences.
+ Specifying caseless matching does not affect these escape sequences.
For example, \p{Lu} always matches only upper case letters.
- The \X escape matches any number of Unicode characters that form an
+ The \X escape matches any number of Unicode characters that form an
extended Unicode sequence. \X is equivalent to
(?>\PM\pM*)
- That is, it matches a character without the "mark" property, followed
- by zero or more characters with the "mark" property, and treats the
- sequence as an atomic group (see below). Characters with the "mark"
+ That is, it matches a character without the "mark" property, followed
+ by zero or more characters with the "mark" property, and treats the
+ sequence as an atomic group (see below). Characters with the "mark"
property are typically accents that affect the preceding character.
- Matching characters by Unicode property is not fast, because PCRE has
- to search a structure that contains data for over fifteen thousand
+ Matching characters by Unicode property is not fast, because PCRE has
+ to search a structure that contains data for over fifteen thousand
characters. That is why the traditional escape sequences such as \d and
\w do not use Unicode properties in PCRE.
Simple assertions
The fourth use of backslash is for certain simple assertions. An asser-
- tion specifies a condition that has to be met at a particular point in
- a match, without consuming any characters from the subject string. The
- use of subpatterns for more complicated assertions is described below.
+ tion specifies a condition that has to be met at a particular point in
+ a match, without consuming any characters from the subject string. The
+ use of subpatterns for more complicated assertions is described below.
The backslashed assertions are:
\b matches at a word boundary
\z matches at end of subject
\G matches at first matching position in subject
- These assertions may not appear in character classes (but note that \b
+ These assertions may not appear in character classes (but note that \b
has a different meaning, namely the backspace character, inside a char-
acter class).
- A word boundary is a position in the subject string where the current
- character and the previous character do not both match \w or \W (i.e.
- one matches \w and the other matches \W), or the start or end of the
+ A word boundary is a position in the subject string where the current
+ character and the previous character do not both match \w or \W (i.e.
+ one matches \w and the other matches \W), or the start or end of the
string if the first or last character matches \w, respectively.
- The \A, \Z, and \z assertions differ from the traditional circumflex
+ The \A, \Z, and \z assertions differ from the traditional circumflex
and dollar (described in the next section) in that they only ever match
- at the very start and end of the subject string, whatever options are
- set. Thus, they are independent of multiline mode. These three asser-
+ at the very start and end of the subject string, whatever options are
+ set. Thus, they are independent of multiline mode. These three asser-
tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which
- affect only the behaviour of the circumflex and dollar metacharacters.
- However, if the startoffset argument of pcre_exec() is non-zero, indi-
+ affect only the behaviour of the circumflex and dollar metacharacters.
+ However, if the startoffset argument of pcre_exec() is non-zero, indi-
cating that matching is to start at a point other than the beginning of
- the subject, \A can never match. The difference between \Z and \z is
- that \Z matches before a newline that is the last character of the
- string as well as at the end of the string, whereas \z matches only at
+ the subject, \A can never match. The difference between \Z and \z is
+ that \Z matches before a newline that is the last character of the
+ string as well as at the end of the string, whereas \z matches only at
the end.
- The \G assertion is true only when the current matching position is at
- the start point of the match, as specified by the startoffset argument
- of pcre_exec(). It differs from \A when the value of startoffset is
- non-zero. By calling pcre_exec() multiple times with appropriate argu-
+ The \G assertion is true only when the current matching position is at
+ the start point of the match, as specified by the startoffset argument
+ of pcre_exec(). It differs from \A when the value of startoffset is
+ non-zero. By calling pcre_exec() multiple times with appropriate argu-
ments, you can mimic Perl's /g option, and it is in this kind of imple-
mentation where \G can be useful.
- Note, however, that PCRE's interpretation of \G, as the start of the
+ Note, however, that PCRE's interpretation of \G, as the start of the
current match, is subtly different from Perl's, which defines it as the
- end of the previous match. In Perl, these can be different when the
- previously matched string was empty. Because PCRE does just one match
+ end of the previous match. In Perl, these can be different when the
+ previously matched string was empty. Because PCRE does just one match
at a time, it cannot reproduce this behaviour.
- If all the alternatives of a pattern begin with \G, the expression is
+ If all the alternatives of a pattern begin with \G, the expression is
anchored to the starting match position, and the "anchored" flag is set
in the compiled regular expression.
CIRCUMFLEX AND DOLLAR
Outside a character class, in the default matching mode, the circumflex
- character is an assertion that is true only if the current matching
- point is at the start of the subject string. If the startoffset argu-
- ment of pcre_exec() is non-zero, circumflex can never match if the
- PCRE_MULTILINE option is unset. Inside a character class, circumflex
+ character is an assertion that is true only if the current matching
+ point is at the start of the subject string. If the startoffset argu-
+ ment of pcre_exec() is non-zero, circumflex can never match if the
+ PCRE_MULTILINE option is unset. Inside a character class, circumflex
has an entirely different meaning (see below).
- Circumflex need not be the first character of the pattern if a number
- of alternatives are involved, but it should be the first thing in each
- alternative in which it appears if the pattern is ever to match that
- branch. If all possible alternatives start with a circumflex, that is,
- if the pattern is constrained to match only at the start of the sub-
- ject, it is said to be an "anchored" pattern. (There are also other
+ Circumflex need not be the first character of the pattern if a number
+ of alternatives are involved, but it should be the first thing in each
+ alternative in which it appears if the pattern is ever to match that
+ branch. If all possible alternatives start with a circumflex, that is,
+ if the pattern is constrained to match only at the start of the sub-
+ ject, it is said to be an "anchored" pattern. (There are also other
constructs that can cause a pattern to be anchored.)
- A dollar character is an assertion that is true only if the current
- matching point is at the end of the subject string, or immediately
+ A dollar character is an assertion that is true only if the current
+ matching point is at the end of the subject string, or immediately
before a newline character that is the last character in the string (by
- default). Dollar need not be the last character of the pattern if a
- number of alternatives are involved, but it should be the last item in
- any branch in which it appears. Dollar has no special meaning in a
+ default). Dollar need not be the last character of the pattern if a
+ number of alternatives are involved, but it should be the last item in
+ any branch in which it appears. Dollar has no special meaning in a
character class.
- The meaning of dollar can be changed so that it matches only at the
- very end of the string, by setting the PCRE_DOLLAR_ENDONLY option at
+ The meaning of dollar can be changed so that it matches only at the
+ very end of the string, by setting the PCRE_DOLLAR_ENDONLY option at
compile time. This does not affect the \Z assertion.
The meanings of the circumflex and dollar characters are changed if the
PCRE_MULTILINE option is set. When this is the case, they match immedi-
- ately after and immediately before an internal newline character,
- respectively, in addition to matching at the start and end of the sub-
- ject string. For example, the pattern /^abc$/ matches the subject
- string "def\nabc" (where \n represents a newline character) in multi-
+ ately after and immediately before an internal newline character,
+ respectively, in addition to matching at the start and end of the sub-
+ ject string. For example, the pattern /^abc$/ matches the subject
+ string "def\nabc" (where \n represents a newline character) in multi-
line mode, but not otherwise. Consequently, patterns that are anchored
- in single line mode because all branches start with ^ are not anchored
- in multiline mode, and a match for circumflex is possible when the
- startoffset argument of pcre_exec() is non-zero. The PCRE_DOL-
+ in single line mode because all branches start with ^ are not anchored
+ in multiline mode, and a match for circumflex is possible when the
+ startoffset argument of pcre_exec() is non-zero. The PCRE_DOL-
LAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
- Note that the sequences \A, \Z, and \z can be used to match the start
- and end of the subject in both modes, and if all branches of a pattern
- start with \A it is always anchored, whether PCRE_MULTILINE is set or
+ Note that the sequences \A, \Z, and \z can be used to match the start
+ and end of the subject in both modes, and if all branches of a pattern
+ start with \A it is always anchored, whether PCRE_MULTILINE is set or
not.
FULL STOP (PERIOD, DOT)
Outside a character class, a dot in the pattern matches any one charac-
- ter in the subject, including a non-printing character, but not (by
- default) newline. In UTF-8 mode, a dot matches any UTF-8 character,
+ ter in the subject, including a non-printing character, but not (by
+ default) newline. In UTF-8 mode, a dot matches any UTF-8 character,
which might be more than one byte long, except (by default) newline. If
- the PCRE_DOTALL option is set, dots match newlines as well. The han-
- dling of dot is entirely independent of the handling of circumflex and
- dollar, the only relationship being that they both involve newline
+ the PCRE_DOTALL option is set, dots match newlines as well. The han-
+ dling of dot is entirely independent of the handling of circumflex and
+ dollar, the only relationship being that they both involve newline
characters. Dot has no special meaning in a character class.
MATCHING A SINGLE BYTE
Outside a character class, the escape sequence \C matches any one byte,
- both in and out of UTF-8 mode. Unlike a dot, it can match a newline.
- The feature is provided in Perl in order to match individual bytes in
- UTF-8 mode. Because it breaks up UTF-8 characters into individual
- bytes, what remains in the string may be a malformed UTF-8 string. For
+ both in and out of UTF-8 mode. Unlike a dot, it can match a newline.
+ The feature is provided in Perl in order to match individual bytes in
+ UTF-8 mode. Because it breaks up UTF-8 characters into individual
+ bytes, what remains in the string may be a malformed UTF-8 string. For
this reason, the \C escape sequence is best avoided.
- PCRE does not allow \C to appear in lookbehind assertions (described
- below), because in UTF-8 mode this would make it impossible to calcu-
+ PCRE does not allow \C to appear in lookbehind assertions (described
+ below), because in UTF-8 mode this would make it impossible to calcu-
late the length of the lookbehind.
An opening square bracket introduces a character class, terminated by a
closing square bracket. A closing square bracket on its own is not spe-
cial. If a closing square bracket is required as a member of the class,
- it should be the first data character in the class (after an initial
+ it should be the first data character in the class (after an initial
circumflex, if present) or escaped with a backslash.
- A character class matches a single character in the subject. In UTF-8
- mode, the character may occupy more than one byte. A matched character
+ A character class matches a single character in the subject. In UTF-8
+ mode, the character may occupy more than one byte. A matched character
must be in the set of characters defined by the class, unless the first
- character in the class definition is a circumflex, in which case the
- subject character must not be in the set defined by the class. If a
- circumflex is actually required as a member of the class, ensure it is
+ character in the class definition is a circumflex, in which case the
+ subject character must not be in the set defined by the class. If a
+ circumflex is actually required as a member of the class, ensure it is
not the first character, or escape it with a backslash.
- For example, the character class [aeiou] matches any lower case vowel,
- while [^aeiou] matches any character that is not a lower case vowel.
+ For example, the character class [aeiou] matches any lower case vowel,
+ while [^aeiou] matches any character that is not a lower case vowel.
Note that a circumflex is just a convenient notation for specifying the
- characters that are in the class by enumerating those that are not. A
- class that starts with a circumflex is not an assertion: it still con-
- sumes a character from the subject string, and therefore it fails if
+ characters that are in the class by enumerating those that are not. A
+ class that starts with a circumflex is not an assertion: it still con-
+ sumes a character from the subject string, and therefore it fails if
the current pointer is at the end of the string.
- In UTF-8 mode, characters with values greater than 255 can be included
- in a class as a literal string of bytes, or by using the \x{ escaping
+ In UTF-8 mode, characters with values greater than 255 can be included
+ in a class as a literal string of bytes, or by using the \x{ escaping
mechanism.
- When caseless matching is set, any letters in a class represent both
- their upper case and lower case versions, so for example, a caseless
- [aeiou] matches "A" as well as "a", and a caseless [^aeiou] does not
- match "A", whereas a caseful version would. When running in UTF-8 mode,
- PCRE supports the concept of case for characters with values greater
- than 128 only when it is compiled with Unicode property support.
+ When caseless matching is set, any letters in a class represent both
+ their upper case and lower case versions, so for example, a caseless
+ [aeiou] matches "A" as well as "a", and a caseless [^aeiou] does not
+ match "A", whereas a caseful version would. In UTF-8 mode, PCRE always
+ understands the concept of case for characters whose values are less
+ than 128, so caseless matching is always possible. For characters with
+ higher values, the concept of case is supported if PCRE is compiled
+ with Unicode property support, but not otherwise. If you want to use
+ caseless matching for characters 128 and above, you must ensure that
+ PCRE is compiled with Unicode property support as well as with UTF-8
+ support.
The newline character is never treated in any special way in character
classes, whatever the setting of the PCRE_DOTALL or PCRE_MULTILINE
gether. A complete description of the interface to the callout function
is given in the pcrecallout documentation.
-Last updated: 09 September 2004
-Copyright (c) 1997-2004 University of Cambridge.
+Last updated: 28 February 2005
+Copyright (c) 1997-2005 University of Cambridge.
git://git.exim.org / exim.git / blobdiff