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diff --git a/gnu/lib/libregex/doc/regex.texi b/gnu/lib/libregex/doc/regex.texi deleted file mode 100644 index d93953e..0000000 --- a/gnu/lib/libregex/doc/regex.texi +++ /dev/null @@ -1,3138 +0,0 @@ -\input texinfo -@c %**start of header -@setfilename regex.info -@settitle Regex -@c %**end of header - -@c \\{fill-paragraph} works better (for me, anyway) if the text in the -@c source file isn't indented. -@paragraphindent 2 - -@c Define a new index for our magic constants. -@defcodeindex cn - -@c Put everything in one index (arbitrarily chosen to be the concept index). -@syncodeindex cn cp -@syncodeindex ky cp -@syncodeindex pg cp -@syncodeindex tp cp -@syncodeindex vr cp - -@c Here is what we use in the Info `dir' file: -@c * Regex: (regex). Regular expression library. - - -@ifinfo -This file documents the GNU regular expression library. - -Copyright (C) 1992, 1993 Free Software Foundation, Inc. - -Permission is granted to make and distribute verbatim copies of this -manual provided the copyright notice and this permission notice are -preserved on all copies. - -@ignore -Permission is granted to process this file through TeX and print the -results, provided the printed document carries a copying permission -notice identical to this one except for the removal of this paragraph -(this paragraph not being relevant to the printed manual). -@end ignore - -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -section entitled ``GNU General Public License'' is included exactly as -in the original, and provided that the entire resulting derived work is -distributed under the terms of a permission notice identical to this one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions, -except that the section entitled ``GNU General Public License'' may be -included in a translation approved by the Free Software Foundation -instead of in the original English. -@end ifinfo - - -@titlepage - -@title Regex -@subtitle edition 0.12a -@subtitle 19 September 1992 -@author Kathryn A. Hargreaves -@author Karl Berry - -@page - -@vskip 0pt plus 1filll -Copyright @copyright{} 1992 Free Software Foundation. - -Permission is granted to make and distribute verbatim copies of this -manual provided the copyright notice and this permission notice are -preserved on all copies. - -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -section entitled ``GNU General Public License'' is included exactly as -in the original, and provided that the entire resulting derived work is -distributed under the terms of a permission notice identical to this -one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions, -except that the section entitled ``GNU General Public License'' may be -included in a translation approved by the Free Software Foundation -instead of in the original English. - -@end titlepage - - -@ifinfo -@node Top, Overview, (dir), (dir) -@top Regular Expression Library - -This manual documents how to program with the GNU regular expression -library. This is edition 0.12a of the manual, 19 September 1992. - -The first part of this master menu lists the major nodes in this Info -document, including the index. The rest of the menu lists all the -lower level nodes in the document. - -@menu -* Overview:: -* Regular Expression Syntax:: -* Common Operators:: -* GNU Operators:: -* GNU Emacs Operators:: -* What Gets Matched?:: -* Programming with Regex:: -* Copying:: Copying and sharing Regex. -* Index:: General index. - --- The Detailed Node Listing --- - -Regular Expression Syntax - -* Syntax Bits:: -* Predefined Syntaxes:: -* Collating Elements vs. Characters:: -* The Backslash Character:: - -Common Operators - -* Match-self Operator:: Ordinary characters. -* Match-any-character Operator:: . -* Concatenation Operator:: Juxtaposition. -* Repetition Operators:: * + ? @{@} -* Alternation Operator:: | -* List Operators:: [...] [^...] -* Grouping Operators:: (...) -* Back-reference Operator:: \digit -* Anchoring Operators:: ^ $ - -Repetition Operators - -* Match-zero-or-more Operator:: * -* Match-one-or-more Operator:: + -* Match-zero-or-one Operator:: ? -* Interval Operators:: @{@} - -List Operators (@code{[} @dots{} @code{]} and @code{[^} @dots{} @code{]}) - -* Character Class Operators:: [:class:] -* Range Operator:: start-end - -Anchoring Operators - -* Match-beginning-of-line Operator:: ^ -* Match-end-of-line Operator:: $ - -GNU Operators - -* Word Operators:: -* Buffer Operators:: - -Word Operators - -* Non-Emacs Syntax Tables:: -* Match-word-boundary Operator:: \b -* Match-within-word Operator:: \B -* Match-beginning-of-word Operator:: \< -* Match-end-of-word Operator:: \> -* Match-word-constituent Operator:: \w -* Match-non-word-constituent Operator:: \W - -Buffer Operators - -* Match-beginning-of-buffer Operator:: \` -* Match-end-of-buffer Operator:: \' - -GNU Emacs Operators - -* Syntactic Class Operators:: - -Syntactic Class Operators - -* Emacs Syntax Tables:: -* Match-syntactic-class Operator:: \sCLASS -* Match-not-syntactic-class Operator:: \SCLASS - -Programming with Regex - -* GNU Regex Functions:: -* POSIX Regex Functions:: -* BSD Regex Functions:: - -GNU Regex Functions - -* GNU Pattern Buffers:: The re_pattern_buffer type. -* GNU Regular Expression Compiling:: re_compile_pattern () -* GNU Matching:: re_match () -* GNU Searching:: re_search () -* Matching/Searching with Split Data:: re_match_2 (), re_search_2 () -* Searching with Fastmaps:: re_compile_fastmap () -* GNU Translate Tables:: The `translate' field. -* Using Registers:: The re_registers type and related fns. -* Freeing GNU Pattern Buffers:: regfree () - -POSIX Regex Functions - -* POSIX Pattern Buffers:: The regex_t type. -* POSIX Regular Expression Compiling:: regcomp () -* POSIX Matching:: regexec () -* Reporting Errors:: regerror () -* Using Byte Offsets:: The regmatch_t type. -* Freeing POSIX Pattern Buffers:: regfree () - -BSD Regex Functions - -* BSD Regular Expression Compiling:: re_comp () -* BSD Searching:: re_exec () -@end menu -@end ifinfo -@node Overview, Regular Expression Syntax, Top, Top -@chapter Overview - -A @dfn{regular expression} (or @dfn{regexp}, or @dfn{pattern}) is a text -string that describes some (mathematical) set of strings. A regexp -@var{r} @dfn{matches} a string @var{s} if @var{s} is in the set of -strings described by @var{r}. - -Using the Regex library, you can: - -@itemize @bullet - -@item -see if a string matches a specified pattern as a whole, and - -@item -search within a string for a substring matching a specified pattern. - -@end itemize - -Some regular expressions match only one string, i.e., the set they -describe has only one member. For example, the regular expression -@samp{foo} matches the string @samp{foo} and no others. Other regular -expressions match more than one string, i.e., the set they describe has -more than one member. For example, the regular expression @samp{f*} -matches the set of strings made up of any number (including zero) of -@samp{f}s. As you can see, some characters in regular expressions match -themselves (such as @samp{f}) and some don't (such as @samp{*}); the -ones that don't match themselves instead let you specify patterns that -describe many different strings. - -To either match or search for a regular expression with the Regex -library functions, you must first compile it with a Regex pattern -compiling function. A @dfn{compiled pattern} is a regular expression -converted to the internal format used by the library functions. Once -you've compiled a pattern, you can use it for matching or searching any -number of times. - -The Regex library consists of two source files: @file{regex.h} and -@file{regex.c}. -@pindex regex.h -@pindex regex.c -Regex provides three groups of functions with which you can operate on -regular expressions. One group---the @sc{gnu} group---is more powerful -but not completely compatible with the other two, namely the @sc{posix} -and Berkeley @sc{unix} groups; its interface was designed specifically -for @sc{gnu}. The other groups have the same interfaces as do the -regular expression functions in @sc{posix} and Berkeley -@sc{unix}. - -We wrote this chapter with programmers in mind, not users of -programs---such as Emacs---that use Regex. We describe the Regex -library in its entirety, not how to write regular expressions that a -particular program understands. - - -@node Regular Expression Syntax, Common Operators, Overview, Top -@chapter Regular Expression Syntax - -@cindex regular expressions, syntax of -@cindex syntax of regular expressions - -@dfn{Characters} are things you can type. @dfn{Operators} are things in -a regular expression that match one or more characters. You compose -regular expressions from operators, which in turn you specify using one -or more characters. - -Most characters represent what we call the match-self operator, i.e., -they match themselves; we call these characters @dfn{ordinary}. Other -characters represent either all or parts of fancier operators; e.g., -@samp{.} represents what we call the match-any-character operator -(which, no surprise, matches (almost) any character); we call these -characters @dfn{special}. Two different things determine what -characters represent what operators: - -@enumerate -@item -the regular expression syntax your program has told the Regex library to -recognize, and - -@item -the context of the character in the regular expression. -@end enumerate - -In the following sections, we describe these things in more detail. - -@menu -* Syntax Bits:: -* Predefined Syntaxes:: -* Collating Elements vs. Characters:: -* The Backslash Character:: -@end menu - - -@node Syntax Bits, Predefined Syntaxes, , Regular Expression Syntax -@section Syntax Bits - -@cindex syntax bits - -In any particular syntax for regular expressions, some characters are -always special, others are sometimes special, and others are never -special. The particular syntax that Regex recognizes for a given -regular expression depends on the value in the @code{syntax} field of -the pattern buffer of that regular expression. - -You get a pattern buffer by compiling a regular expression. @xref{GNU -Pattern Buffers}, and @ref{POSIX Pattern Buffers}, for more information -on pattern buffers. @xref{GNU Regular Expression Compiling}, @ref{POSIX -Regular Expression Compiling}, and @ref{BSD Regular Expression -Compiling}, for more information on compiling. - -Regex considers the value of the @code{syntax} field to be a collection -of bits; we refer to these bits as @dfn{syntax bits}. In most cases, -they affect what characters represent what operators. We describe the -meanings of the operators to which we refer in @ref{Common Operators}, -@ref{GNU Operators}, and @ref{GNU Emacs Operators}. - -For reference, here is the complete list of syntax bits, in alphabetical -order: - -@table @code - -@cnindex RE_BACKSLASH_ESCAPE_IN_LIST -@item RE_BACKSLASH_ESCAPE_IN_LISTS -If this bit is set, then @samp{\} inside a list (@pxref{List Operators} -quotes (makes ordinary, if it's special) the following character; if -this bit isn't set, then @samp{\} is an ordinary character inside lists. -(@xref{The Backslash Character}, for what `\' does outside of lists.) - -@cnindex RE_BK_PLUS_QM -@item RE_BK_PLUS_QM -If this bit is set, then @samp{\+} represents the match-one-or-more -operator and @samp{\?} represents the match-zero-or-more operator; if -this bit isn't set, then @samp{+} represents the match-one-or-more -operator and @samp{?} represents the match-zero-or-one operator. This -bit is irrelevant if @code{RE_LIMITED_OPS} is set. - -@cnindex RE_CHAR_CLASSES -@item RE_CHAR_CLASSES -If this bit is set, then you can use character classes in lists; if this -bit isn't set, then you can't. - -@cnindex RE_CONTEXT_INDEP_ANCHORS -@item RE_CONTEXT_INDEP_ANCHORS -If this bit is set, then @samp{^} and @samp{$} are special anywhere outside -a list; if this bit isn't set, then these characters are special only in -certain contexts. @xref{Match-beginning-of-line Operator}, and -@ref{Match-end-of-line Operator}. - -@cnindex RE_CONTEXT_INDEP_OPS -@item RE_CONTEXT_INDEP_OPS -If this bit is set, then certain characters are special anywhere outside -a list; if this bit isn't set, then those characters are special only in -some contexts and are ordinary elsewhere. Specifically, if this bit -isn't set then @samp{*}, and (if the syntax bit @code{RE_LIMITED_OPS} -isn't set) @samp{+} and @samp{?} (or @samp{\+} and @samp{\?}, depending -on the syntax bit @code{RE_BK_PLUS_QM}) represent repetition operators -only if they're not first in a regular expression or just after an -open-group or alternation operator. The same holds for @samp{@{} (or -@samp{\@{}, depending on the syntax bit @code{RE_NO_BK_BRACES}) if -it is the beginning of a valid interval and the syntax bit -@code{RE_INTERVALS} is set. - -@cnindex RE_CONTEXT_INVALID_OPS -@item RE_CONTEXT_INVALID_OPS -If this bit is set, then repetition and alternation operators can't be -in certain positions within a regular expression. Specifically, the -regular expression is invalid if it has: - -@itemize @bullet - -@item -a repetition operator first in the regular expression or just after a -match-beginning-of-line, open-group, or alternation operator; or - -@item -an alternation operator first or last in the regular expression, just -before a match-end-of-line operator, or just after an alternation or -open-group operator. - -@end itemize - -If this bit isn't set, then you can put the characters representing the -repetition and alternation characters anywhere in a regular expression. -Whether or not they will in fact be operators in certain positions -depends on other syntax bits. - -@cnindex RE_DOT_NEWLINE -@item RE_DOT_NEWLINE -If this bit is set, then the match-any-character operator matches -a newline; if this bit isn't set, then it doesn't. - -@cnindex RE_DOT_NOT_NULL -@item RE_DOT_NOT_NULL -If this bit is set, then the match-any-character operator doesn't match -a null character; if this bit isn't set, then it does. - -@cnindex RE_INTERVALS -@item RE_INTERVALS -If this bit is set, then Regex recognizes interval operators; if this bit -isn't set, then it doesn't. - -@cnindex RE_LIMITED_OPS -@item RE_LIMITED_OPS -If this bit is set, then Regex doesn't recognize the match-one-or-more, -match-zero-or-one or alternation operators; if this bit isn't set, then -it does. - -@cnindex RE_NEWLINE_ALT -@item RE_NEWLINE_ALT -If this bit is set, then newline represents the alternation operator; if -this bit isn't set, then newline is ordinary. - -@cnindex RE_NO_BK_BRACES -@item RE_NO_BK_BRACES -If this bit is set, then @samp{@{} represents the open-interval operator -and @samp{@}} represents the close-interval operator; if this bit isn't -set, then @samp{\@{} represents the open-interval operator and -@samp{\@}} represents the close-interval operator. This bit is relevant -only if @code{RE_INTERVALS} is set. - -@cnindex RE_NO_BK_PARENS -@item RE_NO_BK_PARENS -If this bit is set, then @samp{(} represents the open-group operator and -@samp{)} represents the close-group operator; if this bit isn't set, then -@samp{\(} represents the open-group operator and @samp{\)} represents -the close-group operator. - -@cnindex RE_NO_BK_REFS -@item RE_NO_BK_REFS -If this bit is set, then Regex doesn't recognize @samp{\}@var{digit} as -the back reference operator; if this bit isn't set, then it does. - -@cnindex RE_NO_BK_VBAR -@item RE_NO_BK_VBAR -If this bit is set, then @samp{|} represents the alternation operator; -if this bit isn't set, then @samp{\|} represents the alternation -operator. This bit is irrelevant if @code{RE_LIMITED_OPS} is set. - -@cnindex RE_NO_EMPTY_RANGES -@item RE_NO_EMPTY_RANGES -If this bit is set, then a regular expression with a range whose ending -point collates lower than its starting point is invalid; if this bit -isn't set, then Regex considers such a range to be empty. - -@cnindex RE_UNMATCHED_RIGHT_PAREN_ORD -@item RE_UNMATCHED_RIGHT_PAREN_ORD -If this bit is set and the regular expression has no matching open-group -operator, then Regex considers what would otherwise be a close-group -operator (based on how @code{RE_NO_BK_PARENS} is set) to match @samp{)}. - -@end table - - -@node Predefined Syntaxes, Collating Elements vs. Characters, Syntax Bits, Regular Expression Syntax -@section Predefined Syntaxes - -If you're programming with Regex, you can set a pattern buffer's -(@pxref{GNU Pattern Buffers}, and @ref{POSIX Pattern Buffers}) -@code{syntax} field either to an arbitrary combination of syntax bits -(@pxref{Syntax Bits}) or else to the configurations defined by Regex. -These configurations define the syntaxes used by certain -programs---@sc{gnu} Emacs, -@cindex Emacs -@sc{posix} Awk, -@cindex POSIX Awk -traditional Awk, -@cindex Awk -Grep, -@cindex Grep -@cindex Egrep -Egrep---in addition to syntaxes for @sc{posix} basic and extended -regular expressions. - -The predefined syntaxes--taken directly from @file{regex.h}---are: - -@example -#define RE_SYNTAX_EMACS 0 - -#define RE_SYNTAX_AWK \ - (RE_BACKSLASH_ESCAPE_IN_LISTS | RE_DOT_NOT_NULL \ - | RE_NO_BK_PARENS | RE_NO_BK_REFS \ - | RE_NO_BK_VBAR | RE_NO_EMPTY_RANGES \ - | RE_UNMATCHED_RIGHT_PAREN_ORD) - -#define RE_SYNTAX_POSIX_AWK \ - (RE_SYNTAX_POSIX_EXTENDED | RE_BACKSLASH_ESCAPE_IN_LISTS) - -#define RE_SYNTAX_GREP \ - (RE_BK_PLUS_QM | RE_CHAR_CLASSES \ - | RE_HAT_LISTS_NOT_NEWLINE | RE_INTERVALS \ - | RE_NEWLINE_ALT) - -#define RE_SYNTAX_EGREP \ - (RE_CHAR_CLASSES | RE_CONTEXT_INDEP_ANCHORS \ - | RE_CONTEXT_INDEP_OPS | RE_HAT_LISTS_NOT_NEWLINE \ - | RE_NEWLINE_ALT | RE_NO_BK_PARENS \ - | RE_NO_BK_VBAR) - -#define RE_SYNTAX_POSIX_EGREP \ - (RE_SYNTAX_EGREP | RE_INTERVALS | RE_NO_BK_BRACES) - -/* P1003.2/D11.2, section 4.20.7.1, lines 5078ff. */ -#define RE_SYNTAX_ED RE_SYNTAX_POSIX_BASIC - -#define RE_SYNTAX_SED RE_SYNTAX_POSIX_BASIC - -/* Syntax bits common to both basic and extended POSIX regex syntax. */ -#define _RE_SYNTAX_POSIX_COMMON \ - (RE_CHAR_CLASSES | RE_DOT_NEWLINE | RE_DOT_NOT_NULL \ - | RE_INTERVALS | RE_NO_EMPTY_RANGES) - -#define RE_SYNTAX_POSIX_BASIC \ - (_RE_SYNTAX_POSIX_COMMON | RE_BK_PLUS_QM) - -/* Differs from ..._POSIX_BASIC only in that RE_BK_PLUS_QM becomes - RE_LIMITED_OPS, i.e., \? \+ \| are not recognized. Actually, this - isn't minimal, since other operators, such as \`, aren't disabled. */ -#define RE_SYNTAX_POSIX_MINIMAL_BASIC \ - (_RE_SYNTAX_POSIX_COMMON | RE_LIMITED_OPS) - -#define RE_SYNTAX_POSIX_EXTENDED \ - (_RE_SYNTAX_POSIX_COMMON | RE_CONTEXT_INDEP_ANCHORS \ - | RE_CONTEXT_INDEP_OPS | RE_NO_BK_BRACES \ - | RE_NO_BK_PARENS | RE_NO_BK_VBAR \ - | RE_UNMATCHED_RIGHT_PAREN_ORD) - -/* Differs from ..._POSIX_EXTENDED in that RE_CONTEXT_INVALID_OPS - replaces RE_CONTEXT_INDEP_OPS and RE_NO_BK_REFS is added. */ -#define RE_SYNTAX_POSIX_MINIMAL_EXTENDED \ - (_RE_SYNTAX_POSIX_COMMON | RE_CONTEXT_INDEP_ANCHORS \ - | RE_CONTEXT_INVALID_OPS | RE_NO_BK_BRACES \ - | RE_NO_BK_PARENS | RE_NO_BK_REFS \ - | RE_NO_BK_VBAR | RE_UNMATCHED_RIGHT_PAREN_ORD) -@end example - -@node Collating Elements vs. Characters, The Backslash Character, Predefined Syntaxes, Regular Expression Syntax -@section Collating Elements vs.@: Characters - -@sc{posix} generalizes the notion of a character to that of a -collating element. It defines a @dfn{collating element} to be ``a -sequence of one or more bytes defined in the current collating sequence -as a unit of collation.'' - -This generalizes the notion of a character in -two ways. First, a single character can map into two or more collating -elements. For example, the German -@tex -`\ss' -@end tex -@ifinfo -``es-zet'' -@end ifinfo -collates as the collating element @samp{s} followed by another collating -element @samp{s}. Second, two or more characters can map into one -collating element. For example, the Spanish @samp{ll} collates after -@samp{l} and before @samp{m}. - -Since @sc{posix}'s ``collating element'' preserves the essential idea of -a ``character,'' we use the latter, more familiar, term in this document. - -@node The Backslash Character, , Collating Elements vs. Characters, Regular Expression Syntax -@section The Backslash Character - -@cindex \ -The @samp{\} character has one of four different meanings, depending on -the context in which you use it and what syntax bits are set -(@pxref{Syntax Bits}). It can: 1) stand for itself, 2) quote the next -character, 3) introduce an operator, or 4) do nothing. - -@enumerate -@item -It stands for itself inside a list -(@pxref{List Operators}) if the syntax bit -@code{RE_BACKSLASH_ESCAPE_IN_LISTS} is not set. For example, @samp{[\]} -would match @samp{\}. - -@item -It quotes (makes ordinary, if it's special) the next character when you -use it either: - -@itemize @bullet -@item -outside a list,@footnote{Sometimes -you don't have to explicitly quote special characters to make -them ordinary. For instance, most characters lose any special meaning -inside a list (@pxref{List Operators}). In addition, if the syntax bits -@code{RE_CONTEXT_INVALID_OPS} and @code{RE_CONTEXT_INDEP_OPS} -aren't set, then (for historical reasons) the matcher considers special -characters ordinary if they are in contexts where the operations they -represent make no sense; for example, then the match-zero-or-more -operator (represented by @samp{*}) matches itself in the regular -expression @samp{*foo} because there is no preceding expression on which -it can operate. It is poor practice, however, to depend on this -behavior; if you want a special character to be ordinary outside a list, -it's better to always quote it, regardless.} or - -@item -inside a list and the syntax bit @code{RE_BACKSLASH_ESCAPE_IN_LISTS} is set. - -@end itemize - -@item -It introduces an operator when followed by certain ordinary -characters---sometimes only when certain syntax bits are set. See the -cases @code{RE_BK_PLUS_QM}, @code{RE_NO_BK_BRACES}, @code{RE_NO_BK_VAR}, -@code{RE_NO_BK_PARENS}, @code{RE_NO_BK_REF} in @ref{Syntax Bits}. Also: - -@itemize @bullet -@item -@samp{\b} represents the match-word-boundary operator -(@pxref{Match-word-boundary Operator}). - -@item -@samp{\B} represents the match-within-word operator -(@pxref{Match-within-word Operator}). - -@item -@samp{\<} represents the match-beginning-of-word operator @* -(@pxref{Match-beginning-of-word Operator}). - -@item -@samp{\>} represents the match-end-of-word operator -(@pxref{Match-end-of-word Operator}). - -@item -@samp{\w} represents the match-word-constituent operator -(@pxref{Match-word-constituent Operator}). - -@item -@samp{\W} represents the match-non-word-constituent operator -(@pxref{Match-non-word-constituent Operator}). - -@item -@samp{\`} represents the match-beginning-of-buffer -operator and @samp{\'} represents the match-end-of-buffer operator -(@pxref{Buffer Operators}). - -@item -If Regex was compiled with the C preprocessor symbol @code{emacs} -defined, then @samp{\s@var{class}} represents the match-syntactic-class -operator and @samp{\S@var{class}} represents the -match-not-syntactic-class operator (@pxref{Syntactic Class Operators}). - -@end itemize - -@item -In all other cases, Regex ignores @samp{\}. For example, -@samp{\n} matches @samp{n}. - -@end enumerate - -@node Common Operators, GNU Operators, Regular Expression Syntax, Top -@chapter Common Operators - -You compose regular expressions from operators. In the following -sections, we describe the regular expression operators specified by -@sc{posix}; @sc{gnu} also uses these. Most operators have more than one -representation as characters. @xref{Regular Expression Syntax}, for -what characters represent what operators under what circumstances. - -For most operators that can be represented in two ways, one -representation is a single character and the other is that character -preceded by @samp{\}. For example, either @samp{(} or @samp{\(} -represents the open-group operator. Which one does depends on the -setting of a syntax bit, in this case @code{RE_NO_BK_PARENS}. Why is -this so? Historical reasons dictate some of the varying -representations, while @sc{posix} dictates others. - -Finally, almost all characters lose any special meaning inside a list -(@pxref{List Operators}). - -@menu -* Match-self Operator:: Ordinary characters. -* Match-any-character Operator:: . -* Concatenation Operator:: Juxtaposition. -* Repetition Operators:: * + ? @{@} -* Alternation Operator:: | -* List Operators:: [...] [^...] -* Grouping Operators:: (...) -* Back-reference Operator:: \digit -* Anchoring Operators:: ^ $ -@end menu - -@node Match-self Operator, Match-any-character Operator, , Common Operators -@section The Match-self Operator (@var{ordinary character}) - -This operator matches the character itself. All ordinary characters -(@pxref{Regular Expression Syntax}) represent this operator. For -example, @samp{f} is always an ordinary character, so the regular -expression @samp{f} matches only the string @samp{f}. In -particular, it does @emph{not} match the string @samp{ff}. - -@node Match-any-character Operator, Concatenation Operator, Match-self Operator, Common Operators -@section The Match-any-character Operator (@code{.}) - -@cindex @samp{.} - -This operator matches any single printing or nonprinting character -except it won't match a: - -@table @asis -@item newline -if the syntax bit @code{RE_DOT_NEWLINE} isn't set. - -@item null -if the syntax bit @code{RE_DOT_NOT_NULL} is set. - -@end table - -The @samp{.} (period) character represents this operator. For example, -@samp{a.b} matches any three-character string beginning with @samp{a} -and ending with @samp{b}. - -@node Concatenation Operator, Repetition Operators, Match-any-character Operator, Common Operators -@section The Concatenation Operator - -This operator concatenates two regular expressions @var{a} and @var{b}. -No character represents this operator; you simply put @var{b} after -@var{a}. The result is a regular expression that will match a string if -@var{a} matches its first part and @var{b} matches the rest. For -example, @samp{xy} (two match-self operators) matches @samp{xy}. - -@node Repetition Operators, Alternation Operator, Concatenation Operator, Common Operators -@section Repetition Operators - -Repetition operators repeat the preceding regular expression a specified -number of times. - -@menu -* Match-zero-or-more Operator:: * -* Match-one-or-more Operator:: + -* Match-zero-or-one Operator:: ? -* Interval Operators:: @{@} -@end menu - -@node Match-zero-or-more Operator, Match-one-or-more Operator, , Repetition Operators -@subsection The Match-zero-or-more Operator (@code{*}) - -@cindex @samp{*} - -This operator repeats the smallest possible preceding regular expression -as many times as necessary (including zero) to match the pattern. -@samp{*} represents this operator. For example, @samp{o*} -matches any string made up of zero or more @samp{o}s. Since this -operator operates on the smallest preceding regular expression, -@samp{fo*} has a repeating @samp{o}, not a repeating @samp{fo}. So, -@samp{fo*} matches @samp{f}, @samp{fo}, @samp{foo}, and so on. - -Since the match-zero-or-more operator is a suffix operator, it may be -useless as such when no regular expression precedes it. This is the -case when it: - -@itemize @bullet -@item -is first in a regular expression, or - -@item -follows a match-beginning-of-line, open-group, or alternation -operator. - -@end itemize - -@noindent -Three different things can happen in these cases: - -@enumerate -@item -If the syntax bit @code{RE_CONTEXT_INVALID_OPS} is set, then the -regular expression is invalid. - -@item -If @code{RE_CONTEXT_INVALID_OPS} isn't set, but -@code{RE_CONTEXT_INDEP_OPS} is, then @samp{*} represents the -match-zero-or-more operator (which then operates on the empty string). - -@item -Otherwise, @samp{*} is ordinary. - -@end enumerate - -@cindex backtracking -The matcher processes a match-zero-or-more operator by first matching as -many repetitions of the smallest preceding regular expression as it can. -Then it continues to match the rest of the pattern. - -If it can't match the rest of the pattern, it backtracks (as many times -as necessary), each time discarding one of the matches until it can -either match the entire pattern or be certain that it cannot get a -match. For example, when matching @samp{ca*ar} against @samp{caaar}, -the matcher first matches all three @samp{a}s of the string with the -@samp{a*} of the regular expression. However, it cannot then match the -final @samp{ar} of the regular expression against the final @samp{r} of -the string. So it backtracks, discarding the match of the last @samp{a} -in the string. It can then match the remaining @samp{ar}. - - -@node Match-one-or-more Operator, Match-zero-or-one Operator, Match-zero-or-more Operator, Repetition Operators -@subsection The Match-one-or-more Operator (@code{+} or @code{\+}) - -@cindex @samp{+} - -If the syntax bit @code{RE_LIMITED_OPS} is set, then Regex doesn't recognize -this operator. Otherwise, if the syntax bit @code{RE_BK_PLUS_QM} isn't -set, then @samp{+} represents this operator; if it is, then @samp{\+} -does. - -This operator is similar to the match-zero-or-more operator except that -it repeats the preceding regular expression at least once; -@pxref{Match-zero-or-more Operator}, for what it operates on, how some -syntax bits affect it, and how Regex backtracks to match it. - -For example, supposing that @samp{+} represents the match-one-or-more -operator; then @samp{ca+r} matches, e.g., @samp{car} and -@samp{caaaar}, but not @samp{cr}. - -@node Match-zero-or-one Operator, Interval Operators, Match-one-or-more Operator, Repetition Operators -@subsection The Match-zero-or-one Operator (@code{?} or @code{\?}) -@cindex @samp{?} - -If the syntax bit @code{RE_LIMITED_OPS} is set, then Regex doesn't -recognize this operator. Otherwise, if the syntax bit -@code{RE_BK_PLUS_QM} isn't set, then @samp{?} represents this operator; -if it is, then @samp{\?} does. - -This operator is similar to the match-zero-or-more operator except that -it repeats the preceding regular expression once or not at all; -@pxref{Match-zero-or-more Operator}, to see what it operates on, how -some syntax bits affect it, and how Regex backtracks to match it. - -For example, supposing that @samp{?} represents the match-zero-or-one -operator; then @samp{ca?r} matches both @samp{car} and @samp{cr}, but -nothing else. - -@node Interval Operators, , Match-zero-or-one Operator, Repetition Operators -@subsection Interval Operators (@code{@{} @dots{} @code{@}} or @code{\@{} @dots{} @code{\@}}) - -@cindex interval expression -@cindex @samp{@{} -@cindex @samp{@}} -@cindex @samp{\@{} -@cindex @samp{\@}} - -If the syntax bit @code{RE_INTERVALS} is set, then Regex recognizes -@dfn{interval expressions}. They repeat the smallest possible preceding -regular expression a specified number of times. - -If the syntax bit @code{RE_NO_BK_BRACES} is set, @samp{@{} represents -the @dfn{open-interval operator} and @samp{@}} represents the -@dfn{close-interval operator} ; otherwise, @samp{\@{} and @samp{\@}} do. - -Specifically, supposing that @samp{@{} and @samp{@}} represent the -open-interval and close-interval operators; then: - -@table @code -@item @{@var{count}@} -matches exactly @var{count} occurrences of the preceding regular -expression. - -@item @{@var{min,}@} -matches @var{min} or more occurrences of the preceding regular -expression. - -@item @{@var{min, max}@} -matches at least @var{min} but no more than @var{max} occurrences of -the preceding regular expression. - -@end table - -The interval expression (but not necessarily the regular expression that -contains it) is invalid if: - -@itemize @bullet -@item -@var{min} is greater than @var{max}, or - -@item -any of @var{count}, @var{min}, or @var{max} are outside the range -zero to @code{RE_DUP_MAX} (which symbol @file{regex.h} -defines). - -@end itemize - -If the interval expression is invalid and the syntax bit -@code{RE_NO_BK_BRACES} is set, then Regex considers all the -characters in the would-be interval to be ordinary. If that bit -isn't set, then the regular expression is invalid. - -If the interval expression is valid but there is no preceding regular -expression on which to operate, then if the syntax bit -@code{RE_CONTEXT_INVALID_OPS} is set, the regular expression is invalid. -If that bit isn't set, then Regex considers all the characters---other -than backslashes, which it ignores---in the would-be interval to be -ordinary. - - -@node Alternation Operator, List Operators, Repetition Operators, Common Operators -@section The Alternation Operator (@code{|} or @code{\|}) - -@kindex | -@kindex \| -@cindex alternation operator -@cindex or operator - -If the syntax bit @code{RE_LIMITED_OPS} is set, then Regex doesn't -recognize this operator. Otherwise, if the syntax bit -@code{RE_NO_BK_VBAR} is set, then @samp{|} represents this operator; -otherwise, @samp{\|} does. - -Alternatives match one of a choice of regular expressions: -if you put the character(s) representing the alternation operator between -any two regular expressions @var{a} and @var{b}, the result matches -the union of the strings that @var{a} and @var{b} match. For -example, supposing that @samp{|} is the alternation operator, then -@samp{foo|bar|quux} would match any of @samp{foo}, @samp{bar} or -@samp{quux}. - -@ignore -@c Nobody needs to disallow empty alternatives any more. -If the syntax bit @code{RE_NO_EMPTY_ALTS} is set, then if either of the regular -expressions @var{a} or @var{b} is empty, the -regular expression is invalid. More precisely, if this syntax bit is -set, then the alternation operator can't: - -@itemize @bullet -@item -be first or last in a regular expression; - -@item -follow either another alternation operator or an open-group operator -(@pxref{Grouping Operators}); or - -@item -precede a close-group operator. - -@end itemize - -@noindent -For example, supposing @samp{(} and @samp{)} represent the open and -close-group operators, then @samp{|foo}, @samp{foo|}, @samp{foo||bar}, -@samp{foo(|bar)}, and @samp{(foo|)bar} would all be invalid. -@end ignore - -The alternation operator operates on the @emph{largest} possible -surrounding regular expressions. (Put another way, it has the lowest -precedence of any regular expression operator.) -Thus, the only way you can -delimit its arguments is to use grouping. For example, if @samp{(} and -@samp{)} are the open and close-group operators, then @samp{fo(o|b)ar} -would match either @samp{fooar} or @samp{fobar}. (@samp{foo|bar} would -match @samp{foo} or @samp{bar}.) - -@cindex backtracking -The matcher usually tries all combinations of alternatives so as to -match the longest possible string. For example, when matching -@samp{(fooq|foo)*(qbarquux|bar)} against @samp{fooqbarquux}, it cannot -take, say, the first (``depth-first'') combination it could match, since -then it would be content to match just @samp{fooqbar}. - -@comment xx something about leftmost-longest - - -@node List Operators, Grouping Operators, Alternation Operator, Common Operators -@section List Operators (@code{[} @dots{} @code{]} and @code{[^} @dots{} @code{]}) - -@cindex matching list -@cindex @samp{[} -@cindex @samp{]} -@cindex @samp{^} -@cindex @samp{-} -@cindex @samp{\} -@cindex @samp{[^} -@cindex nonmatching list -@cindex matching newline -@cindex bracket expression - -@dfn{Lists}, also called @dfn{bracket expressions}, are a set of one or -more items. An @dfn{item} is a character, -@ignore -(These get added when they get implemented.) -a collating symbol, an equivalence class expression, -@end ignore -a character class expression, or a range expression. The syntax bits -affect which kinds of items you can put in a list. We explain the last -two items in subsections below. Empty lists are invalid. - -A @dfn{matching list} matches a single character represented by one of -the list items. You form a matching list by enclosing one or more items -within an @dfn{open-matching-list operator} (represented by @samp{[}) -and a @dfn{close-list operator} (represented by @samp{]}). - -For example, @samp{[ab]} matches either @samp{a} or @samp{b}. -@samp{[ad]*} matches the empty string and any string composed of just -@samp{a}s and @samp{d}s in any order. Regex considers invalid a regular -expression with a @samp{[} but no matching -@samp{]}. - -@dfn{Nonmatching lists} are similar to matching lists except that they -match a single character @emph{not} represented by one of the list -items. You use an @dfn{open-nonmatching-list operator} (represented by -@samp{[^}@footnote{Regex therefore doesn't consider the @samp{^} to be -the first character in the list. If you put a @samp{^} character first -in (what you think is) a matching list, you'll turn it into a -nonmatching list.}) instead of an open-matching-list operator to start a -nonmatching list. - -For example, @samp{[^ab]} matches any character except @samp{a} or -@samp{b}. - -If the @code{posix_newline} field in the pattern buffer (@pxref{GNU -Pattern Buffers} is set, then nonmatching lists do not match a newline. - -Most characters lose any special meaning inside a list. The special -characters inside a list follow. - -@table @samp -@item ] -ends the list if it's not the first list item. So, if you want to make -the @samp{]} character a list item, you must put it first. - -@item \ -quotes the next character if the syntax bit @code{RE_BACKSLASH_ESCAPE_IN_LISTS} is -set. - -@ignore -Put these in if they get implemented. - -@item [. -represents the open-collating-symbol operator (@pxref{Collating Symbol -Operators}). - -@item .] -represents the close-collating-symbol operator. - -@item [= -represents the open-equivalence-class operator (@pxref{Equivalence Class -Operators}). - -@item =] -represents the close-equivalence-class operator. - -@end ignore - -@item [: -represents the open-character-class operator (@pxref{Character Class -Operators}) if the syntax bit @code{RE_CHAR_CLASSES} is set and what -follows is a valid character class expression. - -@item :] -represents the close-character-class operator if the syntax bit -@code{RE_CHAR_CLASSES} is set and what precedes it is an -open-character-class operator followed by a valid character class name. - -@item - -represents the range operator (@pxref{Range Operator}) if it's -not first or last in a list or the ending point of a range. - -@end table - -@noindent -All other characters are ordinary. For example, @samp{[.*]} matches -@samp{.} and @samp{*}. - -@menu -* Character Class Operators:: [:class:] -* Range Operator:: start-end -@end menu - -@ignore -(If collating symbols and equivalence class expressions get implemented, -then add this.) - -node Collating Symbol Operators -subsubsection Collating Symbol Operators (@code{[.} @dots{} @code{.]}) - -If the syntax bit @code{XX} is set, then you can represent -collating symbols inside lists. You form a @dfn{collating symbol} by -putting a collating element between an @dfn{open-collating-symbol -operator} and an @dfn{close-collating-symbol operator}. @samp{[.} -represents the open-collating-symbol operator and @samp{.]} represents -the close-collating-symbol operator. For example, if @samp{ll} is a -collating element, then @samp{[[.ll.]]} would match @samp{ll}. - -node Equivalence Class Operators -subsubsection Equivalence Class Operators (@code{[=} @dots{} @code{=]}) -@cindex equivalence class expression in regex -@cindex @samp{[=} in regex -@cindex @samp{=]} in regex - -If the syntax bit @code{XX} is set, then Regex recognizes equivalence class -expressions inside lists. A @dfn{equivalence class expression} is a set -of collating elements which all belong to the same equivalence class. -You form an equivalence class expression by putting a collating -element between an @dfn{open-equivalence-class operator} and a -@dfn{close-equivalence-class operator}. @samp{[=} represents the -open-equivalence-class operator and @samp{=]} represents the -close-equivalence-class operator. For example, if @samp{a} and @samp{A} -were an equivalence class, then both @samp{[[=a=]]} and @samp{[[=A=]]} -would match both @samp{a} and @samp{A}. If the collating element in an -equivalence class expression isn't part of an equivalence class, then -the matcher considers the equivalence class expression to be a collating -symbol. - -@end ignore - -@node Character Class Operators, Range Operator, , List Operators -@subsection Character Class Operators (@code{[:} @dots{} @code{:]}) - -@cindex character classes -@cindex @samp{[:} in regex -@cindex @samp{:]} in regex - -If the syntax bit @code{RE_CHARACTER_CLASSES} is set, then Regex -recognizes character class expressions inside lists. A @dfn{character -class expression} matches one character from a given class. You form a -character class expression by putting a character class name between an -@dfn{open-character-class operator} (represented by @samp{[:}) and a -@dfn{close-character-class operator} (represented by @samp{:]}). The -character class names and their meanings are: - -@table @code - -@item alnum -letters and digits - -@item alpha -letters - -@item blank -system-dependent; for @sc{gnu}, a space or tab - -@item cntrl -control characters (in the @sc{ascii} encoding, code 0177 and codes -less than 040) - -@item digit -digits - -@item graph -same as @code{print} except omits space - -@item lower -lowercase letters - -@item print -printable characters (in the @sc{ascii} encoding, space -tilde---codes 040 through 0176) - -@item punct -neither control nor alphanumeric characters - -@item space -space, carriage return, newline, vertical tab, and form feed - -@item upper -uppercase letters - -@item xdigit -hexadecimal digits: @code{0}--@code{9}, @code{a}--@code{f}, @code{A}--@code{F} - -@end table - -@noindent -These correspond to the definitions in the C library's @file{<ctype.h>} -facility. For example, @samp{[:alpha:]} corresponds to the standard -facility @code{isalpha}. Regex recognizes character class expressions -only inside of lists; so @samp{[[:alpha:]]} matches any letter, but -@samp{[:alpha:]} outside of a bracket expression and not followed by a -repetition operator matches just itself. - -@node Range Operator, , Character Class Operators, List Operators -@subsection The Range Operator (@code{-}) - -Regex recognizes @dfn{range expressions} inside a list. They represent -those characters -that fall between two elements in the current collating sequence. You -form a range expression by putting a @dfn{range operator} between two -@ignore -(If these get implemented, then substitute this for ``characters.'') -of any of the following: characters, collating elements, collating symbols, -and equivalence class expressions. The starting point of the range and -the ending point of the range don't have to be the same kind of item, -e.g., the starting point could be a collating element and the ending -point could be an equivalence class expression. If a range's ending -point is an equivalence class, then all the collating elements in that -class will be in the range. -@end ignore -characters.@footnote{You can't use a character class for the starting -or ending point of a range, since a character class is not a single -character.} @samp{-} represents the range operator. For example, -@samp{a-f} within a list represents all the characters from @samp{a} -through @samp{f} -inclusively. - -If the syntax bit @code{RE_NO_EMPTY_RANGES} is set, then if the range's -ending point collates less than its starting point, the range (and the -regular expression containing it) is invalid. For example, the regular -expression @samp{[z-a]} would be invalid. If this bit isn't set, then -Regex considers such a range to be empty. - -Since @samp{-} represents the range operator, if you want to make a -@samp{-} character itself -a list item, you must do one of the following: - -@itemize @bullet -@item -Put the @samp{-} either first or last in the list. - -@item -Include a range whose starting point collates strictly lower than -@samp{-} and whose ending point collates equal or higher. Unless a -range is the first item in a list, a @samp{-} can't be its starting -point, but @emph{can} be its ending point. That is because Regex -considers @samp{-} to be the range operator unless it is preceded by -another @samp{-}. For example, in the @sc{ascii} encoding, @samp{)}, -@samp{*}, @samp{+}, @samp{,}, @samp{-}, @samp{.}, and @samp{/} are -contiguous characters in the collating sequence. You might think that -@samp{[)-+--/]} has two ranges: @samp{)-+} and @samp{--/}. Rather, it -has the ranges @samp{)-+} and @samp{+--}, plus the character @samp{/}, so -it matches, e.g., @samp{,}, not @samp{.}. - -@item -Put a range whose starting point is @samp{-} first in the list. - -@end itemize - -For example, @samp{[-a-z]} matches a lowercase letter or a hyphen (in -English, in @sc{ascii}). - - -@node Grouping Operators, Back-reference Operator, List Operators, Common Operators -@section Grouping Operators (@code{(} @dots{} @code{)} or @code{\(} @dots{} @code{\)}) - -@kindex ( -@kindex ) -@kindex \( -@kindex \) -@cindex grouping -@cindex subexpressions -@cindex parenthesizing - -A @dfn{group}, also known as a @dfn{subexpression}, consists of an -@dfn{open-group operator}, any number of other operators, and a -@dfn{close-group operator}. Regex treats this sequence as a unit, just -as mathematics and programming languages treat a parenthesized -expression as a unit. - -Therefore, using @dfn{groups}, you can: - -@itemize @bullet -@item -delimit the argument(s) to an alternation operator (@pxref{Alternation -Operator}) or a repetition operator (@pxref{Repetition -Operators}). - -@item -keep track of the indices of the substring that matched a given group. -@xref{Using Registers}, for a precise explanation. -This lets you: - -@itemize @bullet -@item -use the back-reference operator (@pxref{Back-reference Operator}). - -@item -use registers (@pxref{Using Registers}). - -@end itemize - -@end itemize - -If the syntax bit @code{RE_NO_BK_PARENS} is set, then @samp{(} represents -the open-group operator and @samp{)} represents the -close-group operator; otherwise, @samp{\(} and @samp{\)} do. - -If the syntax bit @code{RE_UNMATCHED_RIGHT_PAREN_ORD} is set and a -close-group operator has no matching open-group operator, then Regex -considers it to match @samp{)}. - - -@node Back-reference Operator, Anchoring Operators, Grouping Operators, Common Operators -@section The Back-reference Operator (@dfn{\}@var{digit}) - -@cindex back references - -If the syntax bit @code{RE_NO_BK_REF} isn't set, then Regex recognizes -back references. A back reference matches a specified preceding group. -The back reference operator is represented by @samp{\@var{digit}} -anywhere after the end of a regular expression's @w{@var{digit}-th} -group (@pxref{Grouping Operators}). - -@var{digit} must be between @samp{1} and @samp{9}. The matcher assigns -numbers 1 through 9 to the first nine groups it encounters. By using -one of @samp{\1} through @samp{\9} after the corresponding group's -close-group operator, you can match a substring identical to the -one that the group does. - -Back references match according to the following (in all examples below, -@samp{(} represents the open-group, @samp{)} the close-group, @samp{@{} -the open-interval and @samp{@}} the close-interval operator): - -@itemize @bullet -@item -If the group matches a substring, the back reference matches an -identical substring. For example, @samp{(a)\1} matches @samp{aa} and -@samp{(bana)na\1bo\1} matches @samp{bananabanabobana}. Likewise, -@samp{(.*)\1} matches any (newline-free if the syntax bit -@code{RE_DOT_NEWLINE} isn't set) string that is composed of two -identical halves; the @samp{(.*)} matches the first half and the -@samp{\1} matches the second half. - -@item -If the group matches more than once (as it might if followed -by, e.g., a repetition operator), then the back reference matches the -substring the group @emph{last} matched. For example, -@samp{((a*)b)*\1\2} matches @samp{aabababa}; first @w{group 1} (the -outer one) matches @samp{aab} and @w{group 2} (the inner one) matches -@samp{aa}. Then @w{group 1} matches @samp{ab} and @w{group 2} matches -@samp{a}. So, @samp{\1} matches @samp{ab} and @samp{\2} matches -@samp{a}. - -@item -If the group doesn't participate in a match, i.e., it is part of an -alternative not taken or a repetition operator allows zero repetitions -of it, then the back reference makes the whole match fail. For example, -@samp{(one()|two())-and-(three\2|four\3)} matches @samp{one-and-three} -and @samp{two-and-four}, but not @samp{one-and-four} or -@samp{two-and-three}. For example, if the pattern matches -@samp{one-and-}, then its @w{group 2} matches the empty string and its -@w{group 3} doesn't participate in the match. So, if it then matches -@samp{four}, then when it tries to back reference @w{group 3}---which it -will attempt to do because @samp{\3} follows the @samp{four}---the match -will fail because @w{group 3} didn't participate in the match. - -@end itemize - -You can use a back reference as an argument to a repetition operator. For -example, @samp{(a(b))\2*} matches @samp{a} followed by two or more -@samp{b}s. Similarly, @samp{(a(b))\2@{3@}} matches @samp{abbbb}. - -If there is no preceding @w{@var{digit}-th} subexpression, the regular -expression is invalid. - - -@node Anchoring Operators, , Back-reference Operator, Common Operators -@section Anchoring Operators - -@cindex anchoring -@cindex regexp anchoring - -These operators can constrain a pattern to match only at the beginning or -end of the entire string or at the beginning or end of a line. - -@menu -* Match-beginning-of-line Operator:: ^ -* Match-end-of-line Operator:: $ -@end menu - - -@node Match-beginning-of-line Operator, Match-end-of-line Operator, , Anchoring Operators -@subsection The Match-beginning-of-line Operator (@code{^}) - -@kindex ^ -@cindex beginning-of-line operator -@cindex anchors - -This operator can match the empty string either at the beginning of the -string or after a newline character. Thus, it is said to @dfn{anchor} -the pattern to the beginning of a line. - -In the cases following, @samp{^} represents this operator. (Otherwise, -@samp{^} is ordinary.) - -@itemize @bullet - -@item -It (the @samp{^}) is first in the pattern, as in @samp{^foo}. - -@cnindex RE_CONTEXT_INDEP_ANCHORS @r{(and @samp{^})} -@item -The syntax bit @code{RE_CONTEXT_INDEP_ANCHORS} is set, and it is outside -a bracket expression. - -@cindex open-group operator and @samp{^} -@cindex alternation operator and @samp{^} -@item -It follows an open-group or alternation operator, as in @samp{a\(^b\)} -and @samp{a\|^b}. @xref{Grouping Operators}, and @ref{Alternation -Operator}. - -@end itemize - -These rules imply that some valid patterns containing @samp{^} cannot be -matched; for example, @samp{foo^bar} if @code{RE_CONTEXT_INDEP_ANCHORS} -is set. - -@vindex not_bol @r{field in pattern buffer} -If the @code{not_bol} field is set in the pattern buffer (@pxref{GNU -Pattern Buffers}), then @samp{^} fails to match at the beginning of the -string. @xref{POSIX Matching}, for when you might find this useful. - -@vindex newline_anchor @r{field in pattern buffer} -If the @code{newline_anchor} field is set in the pattern buffer, then -@samp{^} fails to match after a newline. This is useful when you do not -regard the string to be matched as broken into lines. - - -@node Match-end-of-line Operator, , Match-beginning-of-line Operator, Anchoring Operators -@subsection The Match-end-of-line Operator (@code{$}) - -@kindex $ -@cindex end-of-line operator -@cindex anchors - -This operator can match the empty string either at the end of -the string or before a newline character in the string. Thus, it is -said to @dfn{anchor} the pattern to the end of a line. - -It is always represented by @samp{$}. For example, @samp{foo$} usually -matches, e.g., @samp{foo} and, e.g., the first three characters of -@samp{foo\nbar}. - -Its interaction with the syntax bits and pattern buffer fields is -exactly the dual of @samp{^}'s; see the previous section. (That is, -``beginning'' becomes ``end'', ``next'' becomes ``previous'', and -``after'' becomes ``before''.) - - -@node GNU Operators, GNU Emacs Operators, Common Operators, Top -@chapter GNU Operators - -Following are operators that @sc{gnu} defines (and @sc{posix} doesn't). - -@menu -* Word Operators:: -* Buffer Operators:: -@end menu - -@node Word Operators, Buffer Operators, , GNU Operators -@section Word Operators - -The operators in this section require Regex to recognize parts of words. -Regex uses a syntax table to determine whether or not a character is -part of a word, i.e., whether or not it is @dfn{word-constituent}. - -@menu -* Non-Emacs Syntax Tables:: -* Match-word-boundary Operator:: \b -* Match-within-word Operator:: \B -* Match-beginning-of-word Operator:: \< -* Match-end-of-word Operator:: \> -* Match-word-constituent Operator:: \w -* Match-non-word-constituent Operator:: \W -@end menu - -@node Non-Emacs Syntax Tables, Match-word-boundary Operator, , Word Operators -@subsection Non-Emacs Syntax Tables - -A @dfn{syntax table} is an array indexed by the characters in your -character set. In the @sc{ascii} encoding, therefore, a syntax table -has 256 elements. Regex always uses a @code{char *} variable -@code{re_syntax_table} as its syntax table. In some cases, it -initializes this variable and in others it expects you to initialize it. - -@itemize @bullet -@item -If Regex is compiled with the preprocessor symbols @code{emacs} and -@code{SYNTAX_TABLE} both undefined, then Regex allocates -@code{re_syntax_table} and initializes an element @var{i} either to -@code{Sword} (which it defines) if @var{i} is a letter, number, or -@samp{_}, or to zero if it's not. - -@item -If Regex is compiled with @code{emacs} undefined but @code{SYNTAX_TABLE} -defined, then Regex expects you to define a @code{char *} variable -@code{re_syntax_table} to be a valid syntax table. - -@item -@xref{Emacs Syntax Tables}, for what happens when Regex is compiled with -the preprocessor symbol @code{emacs} defined. - -@end itemize - -@node Match-word-boundary Operator, Match-within-word Operator, Non-Emacs Syntax Tables, Word Operators -@subsection The Match-word-boundary Operator (@code{\b}) - -@cindex @samp{\b} -@cindex word boundaries, matching - -This operator (represented by @samp{\b}) matches the empty string at -either the beginning or the end of a word. For example, @samp{\brat\b} -matches the separate word @samp{rat}. - -@node Match-within-word Operator, Match-beginning-of-word Operator, Match-word-boundary Operator, Word Operators -@subsection The Match-within-word Operator (@code{\B}) - -@cindex @samp{\B} - -This operator (represented by @samp{\B}) matches the empty string within -a word. For example, @samp{c\Brat\Be} matches @samp{crate}, but -@samp{dirty \Brat} doesn't match @samp{dirty rat}. - -@node Match-beginning-of-word Operator, Match-end-of-word Operator, Match-within-word Operator, Word Operators -@subsection The Match-beginning-of-word Operator (@code{\<}) - -@cindex @samp{\<} - -This operator (represented by @samp{\<}) matches the empty string at the -beginning of a word. - -@node Match-end-of-word Operator, Match-word-constituent Operator, Match-beginning-of-word Operator, Word Operators -@subsection The Match-end-of-word Operator (@code{\>}) - -@cindex @samp{\>} - -This operator (represented by @samp{\>}) matches the empty string at the -end of a word. - -@node Match-word-constituent Operator, Match-non-word-constituent Operator, Match-end-of-word Operator, Word Operators -@subsection The Match-word-constituent Operator (@code{\w}) - -@cindex @samp{\w} - -This operator (represented by @samp{\w}) matches any word-constituent -character. - -@node Match-non-word-constituent Operator, , Match-word-constituent Operator, Word Operators -@subsection The Match-non-word-constituent Operator (@code{\W}) - -@cindex @samp{\W} - -This operator (represented by @samp{\W}) matches any character that is -not word-constituent. - - -@node Buffer Operators, , Word Operators, GNU Operators -@section Buffer Operators - -Following are operators which work on buffers. In Emacs, a @dfn{buffer} -is, naturally, an Emacs buffer. For other programs, Regex considers the -entire string to be matched as the buffer. - -@menu -* Match-beginning-of-buffer Operator:: \` -* Match-end-of-buffer Operator:: \' -@end menu - - -@node Match-beginning-of-buffer Operator, Match-end-of-buffer Operator, , Buffer Operators -@subsection The Match-beginning-of-buffer Operator (@code{\`}) - -@cindex @samp{\`} - -This operator (represented by @samp{\`}) matches the empty string at the -beginning of the buffer. - -@node Match-end-of-buffer Operator, , Match-beginning-of-buffer Operator, Buffer Operators -@subsection The Match-end-of-buffer Operator (@code{\'}) - -@cindex @samp{\'} - -This operator (represented by @samp{\'}) matches the empty string at the -end of the buffer. - - -@node GNU Emacs Operators, What Gets Matched?, GNU Operators, Top -@chapter GNU Emacs Operators - -Following are operators that @sc{gnu} defines (and @sc{posix} doesn't) -that you can use only when Regex is compiled with the preprocessor -symbol @code{emacs} defined. - -@menu -* Syntactic Class Operators:: -@end menu - - -@node Syntactic Class Operators, , , GNU Emacs Operators -@section Syntactic Class Operators - -The operators in this section require Regex to recognize the syntactic -classes of characters. Regex uses a syntax table to determine this. - -@menu -* Emacs Syntax Tables:: -* Match-syntactic-class Operator:: \sCLASS -* Match-not-syntactic-class Operator:: \SCLASS -@end menu - -@node Emacs Syntax Tables, Match-syntactic-class Operator, , Syntactic Class Operators -@subsection Emacs Syntax Tables - -A @dfn{syntax table} is an array indexed by the characters in your -character set. In the @sc{ascii} encoding, therefore, a syntax table -has 256 elements. - -If Regex is compiled with the preprocessor symbol @code{emacs} defined, -then Regex expects you to define and initialize the variable -@code{re_syntax_table} to be an Emacs syntax table. Emacs' syntax -tables are more complicated than Regex's own (@pxref{Non-Emacs Syntax -Tables}). @xref{Syntax, , Syntax, emacs, The GNU Emacs User's Manual}, -for a description of Emacs' syntax tables. - -@node Match-syntactic-class Operator, Match-not-syntactic-class Operator, Emacs Syntax Tables, Syntactic Class Operators -@subsection The Match-syntactic-class Operator (@code{\s}@var{class}) - -@cindex @samp{\s} - -This operator matches any character whose syntactic class is represented -by a specified character. @samp{\s@var{class}} represents this operator -where @var{class} is the character representing the syntactic class you -want. For example, @samp{w} represents the syntactic -class of word-constituent characters, so @samp{\sw} matches any -word-constituent character. - -@node Match-not-syntactic-class Operator, , Match-syntactic-class Operator, Syntactic Class Operators -@subsection The Match-not-syntactic-class Operator (@code{\S}@var{class}) - -@cindex @samp{\S} - -This operator is similar to the match-syntactic-class operator except -that it matches any character whose syntactic class is @emph{not} -represented by the specified character. @samp{\S@var{class}} represents -this operator. For example, @samp{w} represents the syntactic class of -word-constituent characters, so @samp{\Sw} matches any character that is -not word-constituent. - - -@node What Gets Matched?, Programming with Regex, GNU Emacs Operators, Top -@chapter What Gets Matched? - -Regex usually matches strings according to the ``leftmost longest'' -rule; that is, it chooses the longest of the leftmost matches. This -does not mean that for a regular expression containing subexpressions -that it simply chooses the longest match for each subexpression, left to -right; the overall match must also be the longest possible one. - -For example, @samp{(ac*)(c*d[ac]*)\1} matches @samp{acdacaaa}, not -@samp{acdac}, as it would if it were to choose the longest match for the -first subexpression. - - -@node Programming with Regex, Copying, What Gets Matched?, Top -@chapter Programming with Regex - -Here we describe how you use the Regex data structures and functions in -C programs. Regex has three interfaces: one designed for @sc{gnu}, one -compatible with @sc{posix} and one compatible with Berkeley @sc{unix}. - -@menu -* GNU Regex Functions:: -* POSIX Regex Functions:: -* BSD Regex Functions:: -@end menu - - -@node GNU Regex Functions, POSIX Regex Functions, , Programming with Regex -@section GNU Regex Functions - -If you're writing code that doesn't need to be compatible with either -@sc{posix} or Berkeley @sc{unix}, you can use these functions. They -provide more options than the other interfaces. - -@menu -* GNU Pattern Buffers:: The re_pattern_buffer type. -* GNU Regular Expression Compiling:: re_compile_pattern () -* GNU Matching:: re_match () -* GNU Searching:: re_search () -* Matching/Searching with Split Data:: re_match_2 (), re_search_2 () -* Searching with Fastmaps:: re_compile_fastmap () -* GNU Translate Tables:: The `translate' field. -* Using Registers:: The re_registers type and related fns. -* Freeing GNU Pattern Buffers:: regfree () -@end menu - - -@node GNU Pattern Buffers, GNU Regular Expression Compiling, , GNU Regex Functions -@subsection GNU Pattern Buffers - -@cindex pattern buffer, definition of -@tindex re_pattern_buffer @r{definition} -@tindex struct re_pattern_buffer @r{definition} - -To compile, match, or search for a given regular expression, you must -supply a pattern buffer. A @dfn{pattern buffer} holds one compiled -regular expression.@footnote{Regular expressions are also referred to as -``patterns,'' hence the name ``pattern buffer.''} - -You can have several different pattern buffers simultaneously, each -holding a compiled pattern for a different regular expression. - -@file{regex.h} defines the pattern buffer @code{struct} as follows: - -@example - /* Space that holds the compiled pattern. It is declared as - `unsigned char *' because its elements are - sometimes used as array indexes. */ - unsigned char *buffer; - - /* Number of bytes to which `buffer' points. */ - unsigned long allocated; - - /* Number of bytes actually used in `buffer'. */ - unsigned long used; - - /* Syntax setting with which the pattern was compiled. */ - reg_syntax_t syntax; - - /* Pointer to a fastmap, if any, otherwise zero. re_search uses - the fastmap, if there is one, to skip over impossible - starting points for matches. */ - char *fastmap; - - /* Either a translate table to apply to all characters before - comparing them, or zero for no translation. The translation - is applied to a pattern when it is compiled and to a string - when it is matched. */ - char *translate; - - /* Number of subexpressions found by the compiler. */ - size_t re_nsub; - - /* Zero if this pattern cannot match the empty string, one else. - Well, in truth it's used only in `re_search_2', to see - whether or not we should use the fastmap, so we don't set - this absolutely perfectly; see `re_compile_fastmap' (the - `duplicate' case). */ - unsigned can_be_null : 1; - - /* If REGS_UNALLOCATED, allocate space in the `regs' structure - for `max (RE_NREGS, re_nsub + 1)' groups. - If REGS_REALLOCATE, reallocate space if necessary. - If REGS_FIXED, use what's there. */ -#define REGS_UNALLOCATED 0 -#define REGS_REALLOCATE 1 -#define REGS_FIXED 2 - unsigned regs_allocated : 2; - - /* Set to zero when `regex_compile' compiles a pattern; set to one - by `re_compile_fastmap' if it updates the fastmap. */ - unsigned fastmap_accurate : 1; - - /* If set, `re_match_2' does not return information about - subexpressions. */ - unsigned no_sub : 1; - - /* If set, a beginning-of-line anchor doesn't match at the - beginning of the string. */ - unsigned not_bol : 1; - - /* Similarly for an end-of-line anchor. */ - unsigned not_eol : 1; - - /* If true, an anchor at a newline matches. */ - unsigned newline_anchor : 1; - -@end example - - -@node GNU Regular Expression Compiling, GNU Matching, GNU Pattern Buffers, GNU Regex Functions -@subsection GNU Regular Expression Compiling - -In @sc{gnu}, you can both match and search for a given regular -expression. To do either, you must first compile it in a pattern buffer -(@pxref{GNU Pattern Buffers}). - -@cindex syntax initialization -@vindex re_syntax_options @r{initialization} -Regular expressions match according to the syntax with which they were -compiled; with @sc{gnu}, you indicate what syntax you want by setting -the variable @code{re_syntax_options} (declared in @file{regex.h} and -defined in @file{regex.c}) before calling the compiling function, -@code{re_compile_pattern} (see below). @xref{Syntax Bits}, and -@ref{Predefined Syntaxes}. - -You can change the value of @code{re_syntax_options} at any time. -Usually, however, you set its value once and then never change it. - -@cindex pattern buffer initialization -@code{re_compile_pattern} takes a pattern buffer as an argument. You -must initialize the following fields: - -@table @code - -@item translate @r{initialization} - -@item translate -@vindex translate @r{initialization} -Initialize this to point to a translate table if you want one, or to -zero if you don't. We explain translate tables in @ref{GNU Translate -Tables}. - -@item fastmap -@vindex fastmap @r{initialization} -Initialize this to nonzero if you want a fastmap, or to zero if you -don't. - -@item buffer -@itemx allocated -@vindex buffer @r{initialization} -@vindex allocated @r{initialization} -@findex malloc -If you want @code{re_compile_pattern} to allocate memory for the -compiled pattern, set both of these to zero. If you have an existing -block of memory (allocated with @code{malloc}) you want Regex to use, -set @code{buffer} to its address and @code{allocated} to its size (in -bytes). - -@code{re_compile_pattern} uses @code{realloc} to extend the space for -the compiled pattern as necessary. - -@end table - -To compile a pattern buffer, use: - -@findex re_compile_pattern -@example -char * -re_compile_pattern (const char *@var{regex}, const int @var{regex_size}, - struct re_pattern_buffer *@var{pattern_buffer}) -@end example - -@noindent -@var{regex} is the regular expression's address, @var{regex_size} is its -length, and @var{pattern_buffer} is the pattern buffer's address. - -If @code{re_compile_pattern} successfully compiles the regular -expression, it returns zero and sets @code{*@var{pattern_buffer}} to the -compiled pattern. It sets the pattern buffer's fields as follows: - -@table @code -@item buffer -@vindex buffer @r{field, set by @code{re_compile_pattern}} -to the compiled pattern. - -@item used -@vindex used @r{field, set by @code{re_compile_pattern}} -to the number of bytes the compiled pattern in @code{buffer} occupies. - -@item syntax -@vindex syntax @r{field, set by @code{re_compile_pattern}} -to the current value of @code{re_syntax_options}. - -@item re_nsub -@vindex re_nsub @r{field, set by @code{re_compile_pattern}} -to the number of subexpressions in @var{regex}. - -@item fastmap_accurate -@vindex fastmap_accurate @r{field, set by @code{re_compile_pattern}} -to zero on the theory that the pattern you're compiling is different -than the one previously compiled into @code{buffer}; in that case (since -you can't make a fastmap without a compiled pattern), -@code{fastmap} would either contain an incompatible fastmap, or nothing -at all. - -@c xx what else? -@end table - -If @code{re_compile_pattern} can't compile @var{regex}, it returns an -error string corresponding to one of the errors listed in @ref{POSIX -Regular Expression Compiling}. - - -@node GNU Matching, GNU Searching, GNU Regular Expression Compiling, GNU Regex Functions -@subsection GNU Matching - -@cindex matching with GNU functions - -Matching the @sc{gnu} way means trying to match as much of a string as -possible starting at a position within it you specify. Once you've compiled -a pattern into a pattern buffer (@pxref{GNU Regular Expression -Compiling}), you can ask the matcher to match that pattern against a -string using: - -@findex re_match -@example -int -re_match (struct re_pattern_buffer *@var{pattern_buffer}, - const char *@var{string}, const int @var{size}, - const int @var{start}, struct re_registers *@var{regs}) -@end example - -@noindent -@var{pattern_buffer} is the address of a pattern buffer containing a -compiled pattern. @var{string} is the string you want to match; it can -contain newline and null characters. @var{size} is the length of that -string. @var{start} is the string index at which you want to -begin matching; the first character of @var{string} is at index zero. -@xref{Using Registers}, for a explanation of @var{regs}; you can safely -pass zero. - -@code{re_match} matches the regular expression in @var{pattern_buffer} -against the string @var{string} according to the syntax in -@var{pattern_buffers}'s @code{syntax} field. (@xref{GNU Regular -Expression Compiling}, for how to set it.) The function returns -@math{-1} if the compiled pattern does not match any part of -@var{string} and @math{-2} if an internal error happens; otherwise, it -returns how many (possibly zero) characters of @var{string} the pattern -matched. - -An example: suppose @var{pattern_buffer} points to a pattern buffer -containing the compiled pattern for @samp{a*}, and @var{string} points -to @samp{aaaaab} (whereupon @var{size} should be 6). Then if @var{start} -is 2, @code{re_match} returns 3, i.e., @samp{a*} would have matched the -last three @samp{a}s in @var{string}. If @var{start} is 0, -@code{re_match} returns 5, i.e., @samp{a*} would have matched all the -@samp{a}s in @var{string}. If @var{start} is either 5 or 6, it returns -zero. - -If @var{start} is not between zero and @var{size}, then -@code{re_match} returns @math{-1}. - - -@node GNU Searching, Matching/Searching with Split Data, GNU Matching, GNU Regex Functions -@subsection GNU Searching - -@cindex searching with GNU functions - -@dfn{Searching} means trying to match starting at successive positions -within a string. The function @code{re_search} does this. - -Before calling @code{re_search}, you must compile your regular -expression. @xref{GNU Regular Expression Compiling}. - -Here is the function declaration: - -@findex re_search -@example -int -re_search (struct re_pattern_buffer *@var{pattern_buffer}, - const char *@var{string}, const int @var{size}, - const int @var{start}, const int @var{range}, - struct re_registers *@var{regs}) -@end example - -@noindent -@vindex start @r{argument to @code{re_search}} -@vindex range @r{argument to @code{re_search}} -whose arguments are the same as those to @code{re_match} (@pxref{GNU -Matching}) except that the two arguments @var{start} and @var{range} -replace @code{re_match}'s argument @var{start}. - -If @var{range} is positive, then @code{re_search} attempts a match -starting first at index @var{start}, then at @math{@var{start} + 1} if -that fails, and so on, up to @math{@var{start} + @var{range}}; if -@var{range} is negative, then it attempts a match starting first at -index @var{start}, then at @math{@var{start} -1} if that fails, and so -on. - -If @var{start} is not between zero and @var{size}, then @code{re_search} -returns @math{-1}. When @var{range} is positive, @code{re_search} -adjusts @var{range} so that @math{@var{start} + @var{range} - 1} is -between zero and @var{size}, if necessary; that way it won't search -outside of @var{string}. Similarly, when @var{range} is negative, -@code{re_search} adjusts @var{range} so that @math{@var{start} + -@var{range} + 1} is between zero and @var{size}, if necessary. - -If the @code{fastmap} field of @var{pattern_buffer} is zero, -@code{re_search} matches starting at consecutive positions; otherwise, -it uses @code{fastmap} to make the search more efficient. -@xref{Searching with Fastmaps}. - -If no match is found, @code{re_search} returns @math{-1}. If -a match is found, it returns the index where the match began. If an -internal error happens, it returns @math{-2}. - - -@node Matching/Searching with Split Data, Searching with Fastmaps, GNU Searching, GNU Regex Functions -@subsection Matching and Searching with Split Data - -Using the functions @code{re_match_2} and @code{re_search_2}, you can -match or search in data that is divided into two strings. - -The function: - -@findex re_match_2 -@example -int -re_match_2 (struct re_pattern_buffer *@var{buffer}, - const char *@var{string1}, const int @var{size1}, - const char *@var{string2}, const int @var{size2}, - const int @var{start}, - struct re_registers *@var{regs}, - const int @var{stop}) -@end example - -@noindent -is similar to @code{re_match} (@pxref{GNU Matching}) except that you -pass @emph{two} data strings and sizes, and an index @var{stop} beyond -which you don't want the matcher to try matching. As with -@code{re_match}, if it succeeds, @code{re_match_2} returns how many -characters of @var{string} it matched. Regard @var{string1} and -@var{string2} as concatenated when you set the arguments @var{start} and -@var{stop} and use the contents of @var{regs}; @code{re_match_2} never -returns a value larger than @math{@var{size1} + @var{size2}}. - -The function: - -@findex re_search_2 -@example -int -re_search_2 (struct re_pattern_buffer *@var{buffer}, - const char *@var{string1}, const int @var{size1}, - const char *@var{string2}, const int @var{size2}, - const int @var{start}, const int @var{range}, - struct re_registers *@var{regs}, - const int @var{stop}) -@end example - -@noindent -is similarly related to @code{re_search}. - - -@node Searching with Fastmaps, GNU Translate Tables, Matching/Searching with Split Data, GNU Regex Functions -@subsection Searching with Fastmaps - -@cindex fastmaps -If you're searching through a long string, you should use a fastmap. -Without one, the searcher tries to match at consecutive positions in the -string. Generally, most of the characters in the string could not start -a match. It takes much longer to try matching at a given position in the -string than it does to check in a table whether or not the character at -that position could start a match. A @dfn{fastmap} is such a table. - -More specifically, a fastmap is an array indexed by the characters in -your character set. Under the @sc{ascii} encoding, therefore, a fastmap -has 256 elements. If you want the searcher to use a fastmap with a -given pattern buffer, you must allocate the array and assign the array's -address to the pattern buffer's @code{fastmap} field. You either can -compile the fastmap yourself or have @code{re_search} do it for you; -when @code{fastmap} is nonzero, it automatically compiles a fastmap the -first time you search using a particular compiled pattern. - -To compile a fastmap yourself, use: - -@findex re_compile_fastmap -@example -int -re_compile_fastmap (struct re_pattern_buffer *@var{pattern_buffer}) -@end example - -@noindent -@var{pattern_buffer} is the address of a pattern buffer. If the -character @var{c} could start a match for the pattern, -@code{re_compile_fastmap} makes -@code{@var{pattern_buffer}->fastmap[@var{c}]} nonzero. It returns -@math{0} if it can compile a fastmap and @math{-2} if there is an -internal error. For example, if @samp{|} is the alternation operator -and @var{pattern_buffer} holds the compiled pattern for @samp{a|b}, then -@code{re_compile_fastmap} sets @code{fastmap['a']} and -@code{fastmap['b']} (and no others). - -@code{re_search} uses a fastmap as it moves along in the string: it -checks the string's characters until it finds one that's in the fastmap. -Then it tries matching at that character. If the match fails, it -repeats the process. So, by using a fastmap, @code{re_search} doesn't -waste time trying to match at positions in the string that couldn't -start a match. - -If you don't want @code{re_search} to use a fastmap, -store zero in the @code{fastmap} field of the pattern buffer before -calling @code{re_search}. - -Once you've initialized a pattern buffer's @code{fastmap} field, you -need never do so again---even if you compile a new pattern in -it---provided the way the field is set still reflects whether or not you -want a fastmap. @code{re_search} will still either do nothing if -@code{fastmap} is null or, if it isn't, compile a new fastmap for the -new pattern. - -@node GNU Translate Tables, Using Registers, Searching with Fastmaps, GNU Regex Functions -@subsection GNU Translate Tables - -If you set the @code{translate} field of a pattern buffer to a translate -table, then the @sc{gnu} Regex functions to which you've passed that -pattern buffer use it to apply a simple transformation -to all the regular expression and string characters at which they look. - -A @dfn{translate table} is an array indexed by the characters in your -character set. Under the @sc{ascii} encoding, therefore, a translate -table has 256 elements. The array's elements are also characters in -your character set. When the Regex functions see a character @var{c}, -they use @code{translate[@var{c}]} in its place, with one exception: the -character after a @samp{\} is not translated. (This ensures that, the -operators, e.g., @samp{\B} and @samp{\b}, are always distinguishable.) - -For example, a table that maps all lowercase letters to the -corresponding uppercase ones would cause the matcher to ignore -differences in case.@footnote{A table that maps all uppercase letters to -the corresponding lowercase ones would work just as well for this -purpose.} Such a table would map all characters except lowercase letters -to themselves, and lowercase letters to the corresponding uppercase -ones. Under the @sc{ascii} encoding, here's how you could initialize -such a table (we'll call it @code{case_fold}): - -@example -for (i = 0; i < 256; i++) - case_fold[i] = i; -for (i = 'a'; i <= 'z'; i++) - case_fold[i] = i - ('a' - 'A'); -@end example - -You tell Regex to use a translate table on a given pattern buffer by -assigning that table's address to the @code{translate} field of that -buffer. If you don't want Regex to do any translation, put zero into -this field. You'll get weird results if you change the table's contents -anytime between compiling the pattern buffer, compiling its fastmap, and -matching or searching with the pattern buffer. - -@node Using Registers, Freeing GNU Pattern Buffers, GNU Translate Tables, GNU Regex Functions -@subsection Using Registers - -A group in a regular expression can match a (posssibly empty) substring -of the string that regular expression as a whole matched. The matcher -remembers the beginning and end of the substring matched by -each group. - -To find out what they matched, pass a nonzero @var{regs} argument to a -@sc{gnu} matching or searching function (@pxref{GNU Matching} and -@ref{GNU Searching}), i.e., the address of a structure of this type, as -defined in @file{regex.h}: - -@c We don't bother to include this directly from regex.h, -@c since it changes so rarely. -@example -@tindex re_registers -@vindex num_regs @r{in @code{struct re_registers}} -@vindex start @r{in @code{struct re_registers}} -@vindex end @r{in @code{struct re_registers}} -struct re_registers -@{ - unsigned num_regs; - regoff_t *start; - regoff_t *end; -@}; -@end example - -Except for (possibly) the @var{num_regs}'th element (see below), the -@var{i}th element of the @code{start} and @code{end} arrays records -information about the @var{i}th group in the pattern. (They're declared -as C pointers, but this is only because not all C compilers accept -zero-length arrays; conceptually, it is simplest to think of them as -arrays.) - -The @code{start} and @code{end} arrays are allocated in various ways, -depending on the value of the @code{regs_allocated} -@vindex regs_allocated -field in the pattern buffer passed to the matcher. - -The simplest and perhaps most useful is to let the matcher (re)allocate -enough space to record information for all the groups in the regular -expression. If @code{regs_allocated} is @code{REGS_UNALLOCATED}, -@vindex REGS_UNALLOCATED -the matcher allocates @math{1 + @var{re_nsub}} (another field in the -pattern buffer; @pxref{GNU Pattern Buffers}). The extra element is set -to @math{-1}, and sets @code{regs_allocated} to @code{REGS_REALLOCATE}. -@vindex REGS_REALLOCATE -Then on subsequent calls with the same pattern buffer and @var{regs} -arguments, the matcher reallocates more space if necessary. - -It would perhaps be more logical to make the @code{regs_allocated} field -part of the @code{re_registers} structure, instead of part of the -pattern buffer. But in that case the caller would be forced to -initialize the structure before passing it. Much existing code doesn't -do this initialization, and it's arguably better to avoid it anyway. - -@code{re_compile_pattern} sets @code{regs_allocated} to -@code{REGS_UNALLOCATED}, -so if you use the GNU regular expression -functions, you get this behavior by default. - -xx document re_set_registers - -@sc{posix}, on the other hand, requires a different interface: the -caller is supposed to pass in a fixed-length array which the matcher -fills. Therefore, if @code{regs_allocated} is @code{REGS_FIXED} -@vindex REGS_FIXED -the matcher simply fills that array. - -The following examples illustrate the information recorded in the -@code{re_registers} structure. (In all of them, @samp{(} represents the -open-group and @samp{)} the close-group operator. The first character -in the string @var{string} is at index 0.) - -@c xx i'm not sure this is all true anymore. - -@itemize @bullet - -@item -If the regular expression has an @w{@var{i}-th} -group not contained within another group that matches a -substring of @var{string}, then the function sets -@code{@w{@var{regs}->}start[@var{i}]} to the index in @var{string} where -the substring matched by the @w{@var{i}-th} group begins, and -@code{@w{@var{regs}->}end[@var{i}]} to the index just beyond that -substring's end. The function sets @code{@w{@var{regs}->}start[0]} and -@code{@w{@var{regs}->}end[0]} to analogous information about the entire -pattern. - -For example, when you match @samp{((a)(b))} against @samp{ab}, you get: - -@itemize -@item -0 in @code{@w{@var{regs}->}start[0]} and 2 in @code{@w{@var{regs}->}end[0]} - -@item -0 in @code{@w{@var{regs}->}start[1]} and 2 in @code{@w{@var{regs}->}end[1]} - -@item -0 in @code{@w{@var{regs}->}start[2]} and 1 in @code{@w{@var{regs}->}end[2]} - -@item -1 in @code{@w{@var{regs}->}start[3]} and 2 in @code{@w{@var{regs}->}end[3]} -@end itemize - -@item -If a group matches more than once (as it might if followed by, -e.g., a repetition operator), then the function reports the information -about what the group @emph{last} matched. - -For example, when you match the pattern @samp{(a)*} against the string -@samp{aa}, you get: - -@itemize -@item -0 in @code{@w{@var{regs}->}start[0]} and 2 in @code{@w{@var{regs}->}end[0]} - -@item -1 in @code{@w{@var{regs}->}start[1]} and 2 in @code{@w{@var{regs}->}end[1]} -@end itemize - -@item -If the @w{@var{i}-th} group does not participate in a -successful match, e.g., it is an alternative not taken or a -repetition operator allows zero repetitions of it, then the function -sets @code{@w{@var{regs}->}start[@var{i}]} and -@code{@w{@var{regs}->}end[@var{i}]} to @math{-1}. - -For example, when you match the pattern @samp{(a)*b} against -the string @samp{b}, you get: - -@itemize -@item -0 in @code{@w{@var{regs}->}start[0]} and 1 in @code{@w{@var{regs}->}end[0]} - -@item -@math{-1} in @code{@w{@var{regs}->}start[1]} and @math{-1} in @code{@w{@var{regs}->}end[1]} -@end itemize - -@item -If the @w{@var{i}-th} group matches a zero-length string, then the -function sets @code{@w{@var{regs}->}start[@var{i}]} and -@code{@w{@var{regs}->}end[@var{i}]} to the index just beyond that -zero-length string. - -For example, when you match the pattern @samp{(a*)b} against the string -@samp{b}, you get: - -@itemize -@item -0 in @code{@w{@var{regs}->}start[0]} and 1 in @code{@w{@var{regs}->}end[0]} - -@item -0 in @code{@w{@var{regs}->}start[1]} and 0 in @code{@w{@var{regs}->}end[1]} -@end itemize - -@ignore -The function sets @code{@w{@var{regs}->}start[0]} and -@code{@w{@var{regs}->}end[0]} to analogous information about the entire -pattern. - -For example, when you match the pattern @samp{(a*)} against the empty -string, you get: - -@itemize -@item -0 in @code{@w{@var{regs}->}start[0]} and 0 in @code{@w{@var{regs}->}end[0]} - -@item -0 in @code{@w{@var{regs}->}start[1]} and 0 in @code{@w{@var{regs}->}end[1]} -@end itemize -@end ignore - -@item -If an @w{@var{i}-th} group contains a @w{@var{j}-th} group -in turn not contained within any other group within group @var{i} and -the function reports a match of the @w{@var{i}-th} group, then it -records in @code{@w{@var{regs}->}start[@var{j}]} and -@code{@w{@var{regs}->}end[@var{j}]} the last match (if it matched) of -the @w{@var{j}-th} group. - -For example, when you match the pattern @samp{((a*)b)*} against the -string @samp{abb}, @w{group 2} last matches the empty string, so you -get what it previously matched: - -@itemize -@item -0 in @code{@w{@var{regs}->}start[0]} and 3 in @code{@w{@var{regs}->}end[0]} - -@item -2 in @code{@w{@var{regs}->}start[1]} and 3 in @code{@w{@var{regs}->}end[1]} - -@item -2 in @code{@w{@var{regs}->}start[2]} and 2 in @code{@w{@var{regs}->}end[2]} -@end itemize - -When you match the pattern @samp{((a)*b)*} against the string -@samp{abb}, @w{group 2} doesn't participate in the last match, so you -get: - -@itemize -@item -0 in @code{@w{@var{regs}->}start[0]} and 3 in @code{@w{@var{regs}->}end[0]} - -@item -2 in @code{@w{@var{regs}->}start[1]} and 3 in @code{@w{@var{regs}->}end[1]} - -@item -0 in @code{@w{@var{regs}->}start[2]} and 1 in @code{@w{@var{regs}->}end[2]} -@end itemize - -@item -If an @w{@var{i}-th} group contains a @w{@var{j}-th} group -in turn not contained within any other group within group @var{i} -and the function sets -@code{@w{@var{regs}->}start[@var{i}]} and -@code{@w{@var{regs}->}end[@var{i}]} to @math{-1}, then it also sets -@code{@w{@var{regs}->}start[@var{j}]} and -@code{@w{@var{regs}->}end[@var{j}]} to @math{-1}. - -For example, when you match the pattern @samp{((a)*b)*c} against the -string @samp{c}, you get: - -@itemize -@item -0 in @code{@w{@var{regs}->}start[0]} and 1 in @code{@w{@var{regs}->}end[0]} - -@item -@math{-1} in @code{@w{@var{regs}->}start[1]} and @math{-1} in @code{@w{@var{regs}->}end[1]} - -@item -@math{-1} in @code{@w{@var{regs}->}start[2]} and @math{-1} in @code{@w{@var{regs}->}end[2]} -@end itemize - -@end itemize - -@node Freeing GNU Pattern Buffers, , Using Registers, GNU Regex Functions -@subsection Freeing GNU Pattern Buffers - -To free any allocated fields of a pattern buffer, you can use the -@sc{posix} function described in @ref{Freeing POSIX Pattern Buffers}, -since the type @code{regex_t}---the type for @sc{posix} pattern -buffers---is equivalent to the type @code{re_pattern_buffer}. After -freeing a pattern buffer, you need to again compile a regular expression -in it (@pxref{GNU Regular Expression Compiling}) before passing it to -a matching or searching function. - - -@node POSIX Regex Functions, BSD Regex Functions, GNU Regex Functions, Programming with Regex -@section POSIX Regex Functions - -If you're writing code that has to be @sc{posix} compatible, you'll need -to use these functions. Their interfaces are as specified by @sc{posix}, -draft 1003.2/D11.2. - -@menu -* POSIX Pattern Buffers:: The regex_t type. -* POSIX Regular Expression Compiling:: regcomp () -* POSIX Matching:: regexec () -* Reporting Errors:: regerror () -* Using Byte Offsets:: The regmatch_t type. -* Freeing POSIX Pattern Buffers:: regfree () -@end menu - - -@node POSIX Pattern Buffers, POSIX Regular Expression Compiling, , POSIX Regex Functions -@subsection POSIX Pattern Buffers - -To compile or match a given regular expression the @sc{posix} way, you -must supply a pattern buffer exactly the way you do for @sc{gnu} -(@pxref{GNU Pattern Buffers}). @sc{posix} pattern buffers have type -@code{regex_t}, which is equivalent to the @sc{gnu} pattern buffer -type @code{re_pattern_buffer}. - - -@node POSIX Regular Expression Compiling, POSIX Matching, POSIX Pattern Buffers, POSIX Regex Functions -@subsection POSIX Regular Expression Compiling - -With @sc{posix}, you can only search for a given regular expression; you -can't match it. To do this, you must first compile it in a -pattern buffer, using @code{regcomp}. - -@ignore -Before calling @code{regcomp}, you must initialize this pattern buffer -as you do for @sc{gnu} (@pxref{GNU Regular Expression Compiling}). See -below, however, for how to choose a syntax with which to compile. -@end ignore - -To compile a pattern buffer, use: - -@findex regcomp -@example -int -regcomp (regex_t *@var{preg}, const char *@var{regex}, int @var{cflags}) -@end example - -@noindent -@var{preg} is the initialized pattern buffer's address, @var{regex} is -the regular expression's address, and @var{cflags} is the compilation -flags, which Regex considers as a collection of bits. Here are the -valid bits, as defined in @file{regex.h}: - -@table @code - -@item REG_EXTENDED -@vindex REG_EXTENDED -says to use @sc{posix} Extended Regular Expression syntax; if this isn't -set, then says to use @sc{posix} Basic Regular Expression syntax. -@code{regcomp} sets @var{preg}'s @code{syntax} field accordingly. - -@item REG_ICASE -@vindex REG_ICASE -@cindex ignoring case -says to ignore case; @code{regcomp} sets @var{preg}'s @code{translate} -field to a translate table which ignores case, replacing anything you've -put there before. - -@item REG_NOSUB -@vindex REG_NOSUB -says to set @var{preg}'s @code{no_sub} field; @pxref{POSIX Matching}, -for what this means. - -@item REG_NEWLINE -@vindex REG_NEWLINE -says that a: - -@itemize @bullet - -@item -match-any-character operator (@pxref{Match-any-character -Operator}) doesn't match a newline. - -@item -nonmatching list not containing a newline (@pxref{List -Operators}) matches a newline. - -@item -match-beginning-of-line operator (@pxref{Match-beginning-of-line -Operator}) matches the empty string immediately after a newline, -regardless of how @code{REG_NOTBOL} is set (@pxref{POSIX Matching}, for -an explanation of @code{REG_NOTBOL}). - -@item -match-end-of-line operator (@pxref{Match-beginning-of-line -Operator}) matches the empty string immediately before a newline, -regardless of how @code{REG_NOTEOL} is set (@pxref{POSIX Matching}, -for an explanation of @code{REG_NOTEOL}). - -@end itemize - -@end table - -If @code{regcomp} successfully compiles the regular expression, it -returns zero and sets @code{*@var{pattern_buffer}} to the compiled -pattern. Except for @code{syntax} (which it sets as explained above), it -also sets the same fields the same way as does the @sc{gnu} compiling -function (@pxref{GNU Regular Expression Compiling}). - -If @code{regcomp} can't compile the regular expression, it returns one -of the error codes listed here. (Except when noted differently, the -syntax of in all examples below is basic regular expression syntax.) - -@table @code - -@comment repetitions -@item REG_BADRPT -For example, the consecutive repetition operators @samp{**} in -@samp{a**} are invalid. As another example, if the syntax is extended -regular expression syntax, then the repetition operator @samp{*} with -nothing on which to operate in @samp{*} is invalid. - -@item REG_BADBR -For example, the @var{count} @samp{-1} in @samp{a\@{-1} is invalid. - -@item REG_EBRACE -For example, @samp{a\@{1} is missing a close-interval operator. - -@comment lists -@item REG_EBRACK -For example, @samp{[a} is missing a close-list operator. - -@item REG_ERANGE -For example, the range ending point @samp{z} that collates lower than -does its starting point @samp{a} in @samp{[z-a]} is invalid. Also, the -range with the character class @samp{[:alpha:]} as its starting point in -@samp{[[:alpha:]-|]}. - -@item REG_ECTYPE -For example, the character class name @samp{foo} in @samp{[[:foo:]} is -invalid. - -@comment groups -@item REG_EPAREN -For example, @samp{a\)} is missing an open-group operator and @samp{\(a} -is missing a close-group operator. - -@item REG_ESUBREG -For example, the back reference @samp{\2} that refers to a nonexistent -subexpression in @samp{\(a\)\2} is invalid. - -@comment unfinished business - -@item REG_EEND -Returned when a regular expression causes no other more specific error. - -@item REG_EESCAPE -For example, the trailing backslash @samp{\} in @samp{a\} is invalid, as is the -one in @samp{\}. - -@comment kitchen sink -@item REG_BADPAT -For example, in the extended regular expression syntax, the empty group -@samp{()} in @samp{a()b} is invalid. - -@comment internal -@item REG_ESIZE -Returned when a regular expression needs a pattern buffer larger than -65536 bytes. - -@item REG_ESPACE -Returned when a regular expression makes Regex to run out of memory. - -@end table - - -@node POSIX Matching, Reporting Errors, POSIX Regular Expression Compiling, POSIX Regex Functions -@subsection POSIX Matching - -Matching the @sc{posix} way means trying to match a null-terminated -string starting at its first character. Once you've compiled a pattern -into a pattern buffer (@pxref{POSIX Regular Expression Compiling}), you -can ask the matcher to match that pattern against a string using: - -@findex regexec -@example -int -regexec (const regex_t *@var{preg}, const char *@var{string}, - size_t @var{nmatch}, regmatch_t @var{pmatch}[], int @var{eflags}) -@end example - -@noindent -@var{preg} is the address of a pattern buffer for a compiled pattern. -@var{string} is the string you want to match. - -@xref{Using Byte Offsets}, for an explanation of @var{pmatch}. If you -pass zero for @var{nmatch} or you compiled @var{preg} with the -compilation flag @code{REG_NOSUB} set, then @code{regexec} will ignore -@var{pmatch}; otherwise, you must allocate it to have at least -@var{nmatch} elements. @code{regexec} will record @var{nmatch} byte -offsets in @var{pmatch}, and set to @math{-1} any unused elements up to -@math{@var{pmatch}@code{[@var{nmatch}]} - 1}. - -@var{eflags} specifies @dfn{execution flags}---namely, the two bits -@code{REG_NOTBOL} and @code{REG_NOTEOL} (defined in @file{regex.h}). If -you set @code{REG_NOTBOL}, then the match-beginning-of-line operator -(@pxref{Match-beginning-of-line Operator}) always fails to match. -This lets you match against pieces of a line, as you would need to if, -say, searching for repeated instances of a given pattern in a line; it -would work correctly for patterns both with and without -match-beginning-of-line operators. @code{REG_NOTEOL} works analogously -for the match-end-of-line operator (@pxref{Match-end-of-line -Operator}); it exists for symmetry. - -@code{regexec} tries to find a match for @var{preg} in @var{string} -according to the syntax in @var{preg}'s @code{syntax} field. -(@xref{POSIX Regular Expression Compiling}, for how to set it.) The -function returns zero if the compiled pattern matches @var{string} and -@code{REG_NOMATCH} (defined in @file{regex.h}) if it doesn't. - -@node Reporting Errors, Using Byte Offsets, POSIX Matching, POSIX Regex Functions -@subsection Reporting Errors - -If either @code{regcomp} or @code{regexec} fail, they return a nonzero -error code, the possibilities for which are defined in @file{regex.h}. -@xref{POSIX Regular Expression Compiling}, and @ref{POSIX Matching}, for -what these codes mean. To get an error string corresponding to these -codes, you can use: - -@findex regerror -@example -size_t -regerror (int @var{errcode}, - const regex_t *@var{preg}, - char *@var{errbuf}, - size_t @var{errbuf_size}) -@end example - -@noindent -@var{errcode} is an error code, @var{preg} is the address of the pattern -buffer which provoked the error, @var{errbuf} is the error buffer, and -@var{errbuf_size} is @var{errbuf}'s size. - -@code{regerror} returns the size in bytes of the error string -corresponding to @var{errcode} (including its terminating null). If -@var{errbuf} and @var{errbuf_size} are nonzero, it also returns in -@var{errbuf} the first @math{@var{errbuf_size} - 1} characters of the -error string, followed by a null. -@var{errbuf_size} must be a nonnegative number less than or equal to the -size in bytes of @var{errbuf}. - -You can call @code{regerror} with a null @var{errbuf} and a zero -@var{errbuf_size} to determine how large @var{errbuf} need be to -accommodate @code{regerror}'s error string. - -@node Using Byte Offsets, Freeing POSIX Pattern Buffers, Reporting Errors, POSIX Regex Functions -@subsection Using Byte Offsets - -In @sc{posix}, variables of type @code{regmatch_t} hold analogous -information, but are not identical to, @sc{gnu}'s registers (@pxref{Using -Registers}). To get information about registers in @sc{posix}, pass to -@code{regexec} a nonzero @var{pmatch} of type @code{regmatch_t}, i.e., -the address of a structure of this type, defined in -@file{regex.h}: - -@tindex regmatch_t -@example -typedef struct -@{ - regoff_t rm_so; - regoff_t rm_eo; -@} regmatch_t; -@end example - -When reading in @ref{Using Registers}, about how the matching function -stores the information into the registers, substitute @var{pmatch} for -@var{regs}, @code{@w{@var{pmatch}[@var{i}]->}rm_so} for -@code{@w{@var{regs}->}start[@var{i}]} and -@code{@w{@var{pmatch}[@var{i}]->}rm_eo} for -@code{@w{@var{regs}->}end[@var{i}]}. - -@node Freeing POSIX Pattern Buffers, , Using Byte Offsets, POSIX Regex Functions -@subsection Freeing POSIX Pattern Buffers - -To free any allocated fields of a pattern buffer, use: - -@findex regfree -@example -void -regfree (regex_t *@var{preg}) -@end example - -@noindent -@var{preg} is the pattern buffer whose allocated fields you want freed. -@code{regfree} also sets @var{preg}'s @code{allocated} and @code{used} -fields to zero. After freeing a pattern buffer, you need to again -compile a regular expression in it (@pxref{POSIX Regular Expression -Compiling}) before passing it to the matching function (@pxref{POSIX -Matching}). - - -@node BSD Regex Functions, , POSIX Regex Functions, Programming with Regex -@section BSD Regex Functions - -If you're writing code that has to be Berkeley @sc{unix} compatible, -you'll need to use these functions whose interfaces are the same as those -in Berkeley @sc{unix}. - -@menu -* BSD Regular Expression Compiling:: re_comp () -* BSD Searching:: re_exec () -@end menu - -@node BSD Regular Expression Compiling, BSD Searching, , BSD Regex Functions -@subsection BSD Regular Expression Compiling - -With Berkeley @sc{unix}, you can only search for a given regular -expression; you can't match one. To search for it, you must first -compile it. Before you compile it, you must indicate the regular -expression syntax you want it compiled according to by setting the -variable @code{re_syntax_options} (declared in @file{regex.h} to some -syntax (@pxref{Regular Expression Syntax}). - -To compile a regular expression use: - -@findex re_comp -@example -char * -re_comp (char *@var{regex}) -@end example - -@noindent -@var{regex} is the address of a null-terminated regular expression. -@code{re_comp} uses an internal pattern buffer, so you can use only the -most recently compiled pattern buffer. This means that if you want to -use a given regular expression that you've already compiled---but it -isn't the latest one you've compiled---you'll have to recompile it. If -you call @code{re_comp} with the null string (@emph{not} the empty -string) as the argument, it doesn't change the contents of the pattern -buffer. - -If @code{re_comp} successfully compiles the regular expression, it -returns zero. If it can't compile the regular expression, it returns -an error string. @code{re_comp}'s error messages are identical to those -of @code{re_compile_pattern} (@pxref{GNU Regular Expression -Compiling}). - -@node BSD Searching, , BSD Regular Expression Compiling, BSD Regex Functions -@subsection BSD Searching - -Searching the Berkeley @sc{unix} way means searching in a string -starting at its first character and trying successive positions within -it to find a match. Once you've compiled a pattern using @code{re_comp} -(@pxref{BSD Regular Expression Compiling}), you can ask Regex -to search for that pattern in a string using: - -@findex re_exec -@example -int -re_exec (char *@var{string}) -@end example - -@noindent -@var{string} is the address of the null-terminated string in which you -want to search. - -@code{re_exec} returns either 1 for success or 0 for failure. It -automatically uses a @sc{gnu} fastmap (@pxref{Searching with Fastmaps}). - - -@node Copying, Index, Programming with Regex, Top -@appendix GNU GENERAL PUBLIC LICENSE -@center Version 2, June 1991 - -@display -Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc. -675 Mass Ave, Cambridge, MA 02139, USA - -Everyone is permitted to copy and distribute verbatim copies -of this license document, but changing it is not allowed. -@end display - -@unnumberedsec Preamble - - The licenses for most software are designed to take away your -freedom to share and change it. By contrast, the GNU General Public -License is intended to guarantee your freedom to share and change free -software---to make sure the software is free for all its users. This -General Public License applies to most of the Free Software -Foundation's software and to any other program whose authors commit to -using it. 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You must make sure that they, too, receive or can get the -source code. And you must show them these terms so they know their -rights. - - We protect your rights with two steps: (1) copyright the software, and -(2) offer you this license which gives you legal permission to copy, -distribute and/or modify the software. - - Also, for each author's protection and ours, we want to make certain -that everyone understands that there is no warranty for this free -software. If the software is modified by someone else and passed on, we -want its recipients to know that what they have is not the original, so -that any problems introduced by others will not reflect on the original -authors' reputations. - - Finally, any free program is threatened constantly by software -patents. We wish to avoid the danger that redistributors of a free -program will individually obtain patent licenses, in effect making the -program proprietary. To prevent this, we have made it clear that any -patent must be licensed for everyone's free use or not licensed at all. - - The precise terms and conditions for copying, distribution and -modification follow. - -@iftex -@unnumberedsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION -@end iftex -@ifinfo -@center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION -@end ifinfo - -@enumerate -@item -This License applies to any program or other work which contains -a notice placed by the copyright holder saying it may be distributed -under the terms of this General Public License. The ``Program'', below, -refers to any such program or work, and a ``work based on the Program'' -means either the Program or any derivative work under copyright law: -that is to say, a work containing the Program or a portion of it, -either verbatim or with modifications and/or translated into another -language. (Hereinafter, translation is included without limitation in -the term ``modification''.) Each licensee is addressed as ``you''. - -Activities other than copying, distribution and modification are not -covered by this License; they are outside its scope. The act of -running the Program is not restricted, and the output from the Program -is covered only if its contents constitute a work based on the -Program (independent of having been made by running the Program). -Whether that is true depends on what the Program does. - -@item -You may copy and distribute verbatim copies of the Program's -source code as you receive it, in any medium, provided that you -conspicuously and appropriately publish on each copy an appropriate -copyright notice and disclaimer of warranty; keep intact all the -notices that refer to this License and to the absence of any warranty; -and give any other recipients of the Program a copy of this License -along with the Program. - -You may charge a fee for the physical act of transferring a copy, and -you may at your option offer warranty protection in exchange for a fee. - -@item -You may modify your copy or copies of the Program or any portion -of it, thus forming a work based on the Program, and copy and -distribute such modifications or work under the terms of Section 1 -above, provided that you also meet all of these conditions: - -@enumerate a -@item -You must cause the modified files to carry prominent notices -stating that you changed the files and the date of any change. - -@item -You must cause any work that you distribute or publish, that in -whole or in part contains or is derived from the Program or any -part thereof, to be licensed as a whole at no charge to all third -parties under the terms of this License. - -@item -If the modified program normally reads commands interactively -when run, you must cause it, when started running for such -interactive use in the most ordinary way, to print or display an -announcement including an appropriate copyright notice and a -notice that there is no warranty (or else, saying that you provide -a warranty) and that users may redistribute the program under -these conditions, and telling the user how to view a copy of this -License. (Exception: if the Program itself is interactive but -does not normally print such an announcement, your work based on -the Program is not required to print an announcement.) -@end enumerate - -These requirements apply to the modified work as a whole. If -identifiable sections of that work are not derived from the Program, -and can be reasonably considered independent and separate works in -themselves, then this License, and its terms, do not apply to those -sections when you distribute them as separate works. But when you -distribute the same sections as part of a whole which is a work based -on the Program, the distribution of the whole must be on the terms of -this License, whose permissions for other licensees extend to the -entire whole, and thus to each and every part regardless of who wrote it. - -Thus, it is not the intent of this section to claim rights or contest -your rights to work written entirely by you; rather, the intent is to -exercise the right to control the distribution of derivative or -collective works based on the Program. - -In addition, mere aggregation of another work not based on the Program -with the Program (or with a work based on the Program) on a volume of -a storage or distribution medium does not bring the other work under -the scope of this License. - -@item -You may copy and distribute the Program (or a work based on it, -under Section 2) in object code or executable form under the terms of -Sections 1 and 2 above provided that you also do one of the following: - -@enumerate a -@item -Accompany it with the complete corresponding machine-readable -source code, which must be distributed under the terms of Sections -1 and 2 above on a medium customarily used for software interchange; or, - -@item -Accompany it with a written offer, valid for at least three -years, to give any third party, for a charge no more than your -cost of physically performing source distribution, a complete -machine-readable copy of the corresponding source code, to be -distributed under the terms of Sections 1 and 2 above on a medium -customarily used for software interchange; or, - -@item -Accompany it with the information you received as to the offer -to distribute corresponding source code. (This alternative is -allowed only for noncommercial distribution and only if you -received the program in object code or executable form with such -an offer, in accord with Subsection b above.) -@end enumerate - -The source code for a work means the preferred form of the work for -making modifications to it. For an executable work, complete source -code means all the source code for all modules it contains, plus any -associated interface definition files, plus the scripts used to -control compilation and installation of the executable. However, as a -special exception, the source code distributed need not include -anything that is normally distributed (in either source or binary -form) with the major components (compiler, kernel, and so on) of the -operating system on which the executable runs, unless that component -itself accompanies the executable. - -If distribution of executable or object code is made by offering -access to copy from a designated place, then offering equivalent -access to copy the source code from the same place counts as -distribution of the source code, even though third parties are not -compelled to copy the source along with the object code. - -@item -You may not copy, modify, sublicense, or distribute the Program -except as expressly provided under this License. Any attempt -otherwise to copy, modify, sublicense or distribute the Program is -void, and will automatically terminate your rights under this License. -However, parties who have received copies, or rights, from you under -this License will not have their licenses terminated so long as such -parties remain in full compliance. - -@item -You are not required to accept this License, since you have not -signed it. However, nothing else grants you permission to modify or -distribute the Program or its derivative works. These actions are -prohibited by law if you do not accept this License. Therefore, by -modifying or distributing the Program (or any work based on the -Program), you indicate your acceptance of this License to do so, and -all its terms and conditions for copying, distributing or modifying -the Program or works based on it. - -@item -Each time you redistribute the Program (or any work based on the -Program), the recipient automatically receives a license from the -original licensor to copy, distribute or modify the Program subject to -these terms and conditions. You may not impose any further -restrictions on the recipients' exercise of the rights granted herein. -You are not responsible for enforcing compliance by third parties to -this License. - -@item -If, as a consequence of a court judgment or allegation of patent -infringement or for any other reason (not limited to patent issues), -conditions are imposed on you (whether by court order, agreement or -otherwise) that contradict the conditions of this License, they do not -excuse you from the conditions of this License. If you cannot -distribute so as to satisfy simultaneously your obligations under this -License and any other pertinent obligations, then as a consequence you -may not distribute the Program at all. For example, if a patent -license would not permit royalty-free redistribution of the Program by -all those who receive copies directly or indirectly through you, then -the only way you could satisfy both it and this License would be to -refrain entirely from distribution of the Program. - -If any portion of this section is held invalid or unenforceable under -any particular circumstance, the balance of the section is intended to -apply and the section as a whole is intended to apply in other -circumstances. - -It is not the purpose of this section to induce you to infringe any -patents or other property right claims or to contest validity of any -such claims; this section has the sole purpose of protecting the -integrity of the free software distribution system, which is -implemented by public license practices. Many people have made -generous contributions to the wide range of software distributed -through that system in reliance on consistent application of that -system; it is up to the author/donor to decide if he or she is willing -to distribute software through any other system and a licensee cannot -impose that choice. - -This section is intended to make thoroughly clear what is believed to -be a consequence of the rest of this License. - -@item -If the distribution and/or use of the Program is restricted in -certain countries either by patents or by copyrighted interfaces, the -original copyright holder who places the Program under this License -may add an explicit geographical distribution limitation excluding -those countries, so that distribution is permitted only in or among -countries not thus excluded. In such case, this License incorporates -the limitation as if written in the body of this License. - -@item -The Free Software Foundation may publish revised and/or new versions -of the General Public License from time to time. Such new versions will -be similar in spirit to the present version, but may differ in detail to -address new problems or concerns. - -Each version is given a distinguishing version number. If the Program -specifies a version number of this License which applies to it and ``any -later version'', you have the option of following the terms and conditions -either of that version or of any later version published by the Free -Software Foundation. If the Program does not specify a version number of -this License, you may choose any version ever published by the Free Software -Foundation. - -@item -If you wish to incorporate parts of the Program into other free -programs whose distribution conditions are different, write to the author -to ask for permission. For software which is copyrighted by the Free -Software Foundation, write to the Free Software Foundation; we sometimes -make exceptions for this. Our decision will be guided by the two goals -of preserving the free status of all derivatives of our free software and -of promoting the sharing and reuse of software generally. - -@iftex -@heading NO WARRANTY -@end iftex -@ifinfo -@center NO WARRANTY -@end ifinfo - -@item -BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY -FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN -OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES -PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED -OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF -MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS -TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE -PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, -REPAIR OR CORRECTION. - -@item -IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING -WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR -REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, -INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING -OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED -TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY -YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER -PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE -POSSIBILITY OF SUCH DAMAGES. -@end enumerate - -@iftex -@heading END OF TERMS AND CONDITIONS -@end iftex -@ifinfo -@center END OF TERMS AND CONDITIONS -@end ifinfo - -@page -@unnumberedsec Appendix: How to Apply These Terms to Your New Programs - - If you develop a new program, and you want it to be of the greatest -possible use to the public, the best way to achieve this is to make it -free software which everyone can redistribute and change under these terms. - - To do so, attach the following notices to the program. It is safest -to attach them to the start of each source file to most effectively -convey the exclusion of warranty; and each file should have at least -the ``copyright'' line and a pointer to where the full notice is found. - -@smallexample -@var{one line to give the program's name and a brief idea of what it does.} -Copyright (C) 19@var{yy} @var{name of author} - -This program is free software; you can redistribute it and/or modify -it under the terms of the GNU General Public License as published by -the Free Software Foundation; either version 2 of the License, or -(at your option) any later version. - -This program is distributed in the hope that it will be useful, -but WITHOUT ANY WARRANTY; without even the implied warranty of -MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the -GNU General Public License for more details. - -You should have received a copy of the GNU General Public License -along with this program; if not, write to the Free Software -Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. -@end smallexample - -Also add information on how to contact you by electronic and paper mail. - -If the program is interactive, make it output a short notice like this -when it starts in an interactive mode: - -@smallexample -Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author} -Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. -This is free software, and you are welcome to redistribute it -under certain conditions; type `show c' for details. -@end smallexample - -The hypothetical commands @samp{show w} and @samp{show c} should show -the appropriate parts of the General Public License. Of course, the -commands you use may be called something other than @samp{show w} and -@samp{show c}; they could even be mouse-clicks or menu items---whatever -suits your program. - -You should also get your employer (if you work as a programmer) or your -school, if any, to sign a ``copyright disclaimer'' for the program, if -necessary. Here is a sample; alter the names: - -@example -Yoyodyne, Inc., hereby disclaims all copyright interest in the program -`Gnomovision' (which makes passes at compilers) written by James Hacker. - -@var{signature of Ty Coon}, 1 April 1989 -Ty Coon, President of Vice -@end example - -This General Public License does not permit incorporating your program into -proprietary programs. If your program is a subroutine library, you may -consider it more useful to permit linking proprietary applications with the -library. If this is what you want to do, use the GNU Library General -Public License instead of this License. - - -@node Index, , Copying, Top -@unnumbered Index - -@printindex cp - -@contents - -@bye |
