diff options
Diffstat (limited to 'man7/regex.7')
| -rw-r--r-- | man7/regex.7 | 293 |
1 files changed, 0 insertions, 293 deletions
diff --git a/man7/regex.7 b/man7/regex.7 deleted file mode 100644 index ad63573..0000000 --- a/man7/regex.7 +++ /dev/null @@ -1,293 +0,0 @@ -'\" t -.\" From Henry Spencer's regex package (as found in the apache -.\" distribution). The package carries the following copyright: -.\" -.\" Copyright 1992, 1993, 1994 Henry Spencer. All rights reserved. -.\" %%%LICENSE_START(MISC) -.\" This software is not subject to any license of the American Telephone -.\" and Telegraph Company or of the Regents of the University of California. -.\" -.\" Permission is granted to anyone to use this software for any purpose -.\" on any computer system, and to alter it and redistribute it, subject -.\" to the following restrictions: -.\" -.\" 1. The author is not responsible for the consequences of use of this -.\" software, no matter how awful, even if they arise from flaws in it. -.\" -.\" 2. The origin of this software must not be misrepresented, either by -.\" explicit claim or by omission. Since few users ever read sources, -.\" credits must appear in the documentation. -.\" -.\" 3. Altered versions must be plainly marked as such, and must not be -.\" misrepresented as being the original software. Since few users -.\" ever read sources, credits must appear in the documentation. -.\" -.\" 4. This notice may not be removed or altered. -.\" %%%LICENSE_END -.\" -.\" In order to comply with `credits must appear in the documentation' -.\" I added an AUTHOR paragraph below - aeb. -.\" -.\" In the default nroff environment there is no dagger \(dg. -.\" -.\" 2005-05-11 Removed discussion of `[[:<:]]' and `[[:>:]]', which -.\" appear not to be in the glibc implementation of regcomp -.\" -.ie t .ds dg \(dg -.el .ds dg (!) -.TH regex 7 2023-11-01 "Linux man-pages 6.7" -.SH NAME -regex \- POSIX.2 regular expressions -.SH DESCRIPTION -Regular expressions ("RE"s), -as defined in POSIX.2, come in two forms: -modern REs (roughly those of -.BR egrep (1); -POSIX.2 calls these "extended" REs) -and obsolete REs (roughly those of -.BR ed (1); -POSIX.2 "basic" REs). -Obsolete REs mostly exist for backward compatibility in some old programs; -they will be discussed at the end. -POSIX.2 leaves some aspects of RE syntax and semantics open; -"\*(dg" marks decisions on these aspects that -may not be fully portable to other POSIX.2 implementations. -.P -A (modern) RE is one\*(dg or more nonempty\*(dg \fIbranches\fR, -separated by \[aq]|\[aq]. -It matches anything that matches one of the branches. -.P -A branch is one\*(dg or more \fIpieces\fR, concatenated. -It matches a match for the first, followed by a match for the second, -and so on. -.P -A piece is an \fIatom\fR possibly followed -by a single\*(dg \[aq]*\[aq], \[aq]+\[aq], \[aq]?\[aq], or \fIbound\fR. -An atom followed by \[aq]*\[aq] -matches a sequence of 0 or more matches of the atom. -An atom followed by \[aq]+\[aq] -matches a sequence of 1 or more matches of the atom. -An atom followed by \[aq]?\[aq] -matches a sequence of 0 or 1 matches of the atom. -.P -A \fIbound\fR is \[aq]{\[aq] followed by an unsigned decimal integer, -possibly followed by \[aq],\[aq] -possibly followed by another unsigned decimal integer, -always followed by \[aq]}\[aq]. -The integers must lie between 0 and -.B RE_DUP_MAX -(255\*(dg) inclusive, -and if there are two of them, the first may not exceed the second. -An atom followed by a bound containing one integer \fIi\fR -and no comma matches -a sequence of exactly \fIi\fR matches of the atom. -An atom followed by a bound -containing one integer \fIi\fR and a comma matches -a sequence of \fIi\fR or more matches of the atom. -An atom followed by a bound -containing two integers \fIi\fR and \fIj\fR matches -a sequence of \fIi\fR through \fIj\fR (inclusive) matches of the atom. -.P -An atom is a regular expression enclosed in "\fI()\fP" -(matching a match for the regular expression), -an empty set of "\fI()\fP" (matching the null string)\*(dg, -a \fIbracket expression\fR (see below), -\[aq].\[aq] (matching any single character), -\[aq]\[ha]\[aq] (matching the null string at the beginning of a line), -\[aq]$\[aq] (matching the null string at the end of a line), -a \[aq]\e\[aq] followed by one of the characters "\fI\[ha].[$()|*+?{\e\fP" -(matching that character taken as an ordinary character), -a \[aq]\e\[aq] followed by any other character\*(dg -(matching that character taken as an ordinary character, -as if the \[aq]\e\[aq] had not been present\*(dg), -or a single character with no other significance (matching that character). -A \[aq]{\[aq] followed by a character other than a digit -is an ordinary character, -not the beginning of a bound\*(dg. -It is illegal to end an RE with \[aq]\e\[aq]. -.P -A \fIbracket expression\fR is a list of characters enclosed in "\fI[]\fP". -It normally matches any single character from the list (but see below). -If the list begins with \[aq]\[ha]\[aq], -it matches any single character -(but see below) \fInot\fR from the rest of the list. -If two characters in the list are separated by \[aq]\-\[aq], this is shorthand -for the full \fIrange\fR of characters between those two (inclusive) in the -collating sequence, -for example, "\fI[0\-9]\fP" in ASCII matches any decimal digit. -It is illegal\*(dg for two ranges to share an -endpoint, for example, "\fIa\-c\-e\fP". -Ranges are very collating-sequence-dependent, -and portable programs should avoid relying on them. -.P -To include a literal \[aq]]\[aq] in the list, make it the first character -(following a possible \[aq]\[ha]\[aq]). -To include a literal \[aq]\-\[aq], make it the first or last character, -or the second endpoint of a range. -To use a literal \[aq]\-\[aq] as the first endpoint of a range, -enclose it in "\fI[.\fP" and "\fI.]\fP" -to make it a collating element (see below). -With the exception of these and some combinations using \[aq][\[aq] (see next -paragraphs), all other special characters, including \[aq]\e\[aq], lose their -special significance within a bracket expression. -.P -Within a bracket expression, a collating element (a character, -a multicharacter sequence that collates as if it were a single character, -or a collating-sequence name for either) -enclosed in "\fI[.\fP" and "\fI.]\fP" stands for the -sequence of characters of that collating element. -The sequence is a single element of the bracket expression's list. -A bracket expression containing a multicharacter collating element -can thus match more than one character, -for example, if the collating sequence includes a "ch" collating element, -then the RE "\fI[[.ch.]]*c\fP" matches the first five characters -of "chchcc". -.P -Within a bracket expression, a collating element enclosed in "\fI[=\fP" and -"\fI=]\fP" is an equivalence class, standing for the sequences of characters -of all collating elements equivalent to that one, including itself. -(If there are no other equivalent collating elements, -the treatment is as if the enclosing delimiters -were "\fI[.\fP" and "\fI.]\fP".) -For example, if o and \(^o are the members of an equivalence class, -then "\fI[[=o=]]\fP", "\fI[[=\(^o=]]\fP", -and "\fI[o\(^o]\fP" are all synonymous. -An equivalence class may not\*(dg be an endpoint -of a range. -.P -Within a bracket expression, the name of a \fIcharacter class\fR enclosed -in "\fI[:\fP" and "\fI:]\fP" stands for the list -of all characters belonging to that -class. -Standard character class names are: -.P -.RS -.TS -l l l. -alnum digit punct -alpha graph space -blank lower upper -cntrl print xdigit -.TE -.RE -.P -These stand for the character classes defined in -.BR wctype (3). -A locale may provide others. -A character class may not be used as an endpoint of a range. -.\" As per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=295666 -.\" The following does not seem to apply in the glibc implementation -.\" .P -.\" There are two special cases\*(dg of bracket expressions: -.\" the bracket expressions "\fI[[:<:]]\fP" and "\fI[[:>:]]\fP" match -.\" the null string at the beginning and end of a word respectively. -.\" A word is defined as a sequence of -.\" word characters -.\" which is neither preceded nor followed by -.\" word characters. -.\" A word character is an -.\" .I alnum -.\" character (as defined by -.\" .BR wctype (3)) -.\" or an underscore. -.\" This is an extension, -.\" compatible with but not specified by POSIX.2, -.\" and should be used with -.\" caution in software intended to be portable to other systems. -.P -In the event that an RE could match more than one substring of a given -string, -the RE matches the one starting earliest in the string. -If the RE could match more than one substring starting at that point, -it matches the longest. -Subexpressions also match the longest possible substrings, subject to -the constraint that the whole match be as long as possible, -with subexpressions starting earlier in the RE taking priority over -ones starting later. -Note that higher-level subexpressions thus take priority over -their lower-level component subexpressions. -.P -Match lengths are measured in characters, not collating elements. -A null string is considered longer than no match at all. -For example, -"\fIbb*\fP" matches the three middle characters of "abbbc", -"\fI(wee|week)(knights|nights)\fP" -matches all ten characters of "weeknights", -when "\fI(.*).*\fP" is matched against "abc" the parenthesized subexpression -matches all three characters, and -when "\fI(a*)*\fP" is matched against "bc" -both the whole RE and the parenthesized -subexpression match the null string. -.P -If case-independent matching is specified, -the effect is much as if all case distinctions had vanished from the -alphabet. -When an alphabetic that exists in multiple cases appears as an -ordinary character outside a bracket expression, it is effectively -transformed into a bracket expression containing both cases, -for example, \[aq]x\[aq] becomes "\fI[xX]\fP". -When it appears inside a bracket expression, all case counterparts -of it are added to the bracket expression, so that, for example, "\fI[x]\fP" -becomes "\fI[xX]\fP" and "\fI[\[ha]x]\fP" becomes "\fI[\[ha]xX]\fP". -.P -No particular limit is imposed on the length of REs\*(dg. -Programs intended to be portable should not employ REs longer -than 256 bytes, -as an implementation can refuse to accept such REs and remain -POSIX-compliant. -.P -Obsolete ("basic") regular expressions differ in several respects. -\[aq]|\[aq], \[aq]+\[aq], and \[aq]?\[aq] are -ordinary characters and there is no equivalent -for their functionality. -The delimiters for bounds are "\fI\e{\fP" and "\fI\e}\fP", -with \[aq]{\[aq] and \[aq]}\[aq] by themselves ordinary characters. -The parentheses for nested subexpressions are "\fI\e(\fP" and "\fI\e)\fP", -with \[aq](\[aq] and \[aq])\[aq] by themselves ordinary characters. -\[aq]\[ha]\[aq] is an ordinary character except at the beginning of the -RE or\*(dg the beginning of a parenthesized subexpression, -\[aq]$\[aq] is an ordinary character except at the end of the -RE or\*(dg the end of a parenthesized subexpression, -and \[aq]*\[aq] is an ordinary character if it appears at the beginning of the -RE or the beginning of a parenthesized subexpression -(after a possible leading \[aq]\[ha]\[aq]). -.P -Finally, there is one new type of atom, a \fIback reference\fR: -\[aq]\e\[aq] followed by a nonzero decimal digit \fId\fR -matches the same sequence of characters -matched by the \fId\fRth parenthesized subexpression -(numbering subexpressions by the positions of their opening parentheses, -left to right), -so that, for example, "\fI\e([bc]\e)\e1\fP" matches "bb" or "cc" but not "bc". -.SH BUGS -Having two kinds of REs is a botch. -.P -The current POSIX.2 spec says that \[aq])\[aq] is an ordinary character in -the absence of an unmatched \[aq](\[aq]; -this was an unintentional result of a wording error, -and change is likely. -Avoid relying on it. -.P -Back references are a dreadful botch, -posing major problems for efficient implementations. -They are also somewhat vaguely defined -(does -"\fIa\e(\e(b\e)*\e2\e)*d\fP" match "abbbd"?). -Avoid using them. -.P -POSIX.2's specification of case-independent matching is vague. -The "one case implies all cases" definition given above -is current consensus among implementors as to the right interpretation. -.\" As per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=295666 -.\" The following does not seem to apply in the glibc implementation -.\" .P -.\" The syntax for word boundaries is incredibly ugly. -.SH AUTHOR -.\" Sigh... The page license means we must have the author's name -.\" in the formatted output. -This page was taken from Henry Spencer's regex package. -.SH SEE ALSO -.BR grep (1), -.BR regex (3) -.P -POSIX.2, section 2.8 (Regular Expression Notation). |