'\" '\" Copyright (c) 1993 The Regents of the University of California. '\" Copyright (c) 1994-1996 Sun Microsystems, Inc. '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" '\" SCCS: @(#) regexp.n 1.11 96/03/25 20:21:48 '\" '\" The definitions below are for supplemental macros used in Tcl/Tk '\" manual entries. '\" '\" .AP type name in/out ?indent? '\" Start paragraph describing an argument to a library procedure. '\" type is type of argument (int, etc.), in/out is either "in", "out", '\" or "in/out" to describe whether procedure reads or modifies arg, '\" and indent is equivalent to second arg of .IP (shouldn't ever be '\" needed; use .AS below instead) '\" '\" .AS ?type? ?name? '\" Give maximum sizes of arguments for setting tab stops. Type and '\" name are examples of largest possible arguments that will be passed '\" to .AP later. If args are omitted, default tab stops are used. '\" '\" .BS '\" Start box enclosure. From here until next .BE, everything will be '\" enclosed in one large box. '\" '\" .BE '\" End of box enclosure. '\" '\" .CS '\" Begin code excerpt. '\" '\" .CE '\" End code excerpt. '\" '\" .VS ?br? '\" Begin vertical sidebar, for use in marking newly-changed parts '\" of man pages. If an argument is present, then a line break is '\" forced before starting the sidebar. '\" '\" .VE '\" End of vertical sidebar. '\" '\" .DS '\" Begin an indented unfilled display. '\" '\" .DE '\" End of indented unfilled display. '\" '\" .SO '\" Start of list of standard options for a Tk widget. The '\" options follow on successive lines, in four columns separated '\" by tabs. '\" '\" .SE '\" End of list of standard options for a Tk widget. '\" '\" .OP cmdName dbName dbClass '\" Start of description of a specific option. cmdName gives the '\" option's name as specified in the class command, dbName gives '\" the option's name in the option database, and dbClass gives '\" the option's class in the option database. '\" '\" .UL arg1 arg2 '\" Print arg1 underlined, then print arg2 normally. '\" '\" SCCS: @(#) man.macros 1.8 96/02/15 20:02:24 '\" '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. .if t .wh -1.3i ^B .nr ^l \n(.l .ad b '\" # Start an argument description .de AP .ie !"\\$4"" .TP \\$4 .el \{\ . ie !"\\$2"" .TP \\n()Cu . el .TP 15 .\} .ie !"\\$3"" \{\ .ta \\n()Au \\n()Bu \&\\$1 \\fI\\$2\\fP (\\$3) .\".b .\} .el \{\ .br .ie !"\\$2"" \{\ \&\\$1 \\fI\\$2\\fP .\} .el \{\ \&\\fI\\$1\\fP .\} .\} .. '\" # define tabbing values for .AP .de AS .nr )A 10n .if !"\\$1"" .nr )A \\w'\\$1'u+3n .nr )B \\n()Au+15n .\" .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n .nr )C \\n()Bu+\\w'(in/out)'u+2n .. .AS Tcl_Interp Tcl_CreateInterp in/out '\" # BS - start boxed text '\" # ^y = starting y location '\" # ^b = 1 .de BS .br .mk ^y .nr ^b 1u .if n .nf .if n .ti 0 .if n \l'\\n(.lu\(ul' .if n .fi .. '\" # BE - end boxed text (draw box now) .de BE .nf .ti 0 .mk ^t .ie n \l'\\n(^lu\(ul' .el \{\ .\" Draw four-sided box normally, but don't draw top of .\" box if the box started on an earlier page. .ie !\\n(^b-1 \{\ \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .el \}\ \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .\} .fi .br .nr ^b 0 .. '\" # VS - start vertical sidebar '\" # ^Y = starting y location '\" # ^v = 1 (for troff; for nroff this doesn't matter) .de VS .if !"\\$1"" .br .mk ^Y .ie n 'mc \s12\(br\s0 .el .nr ^v 1u .. '\" # VE - end of vertical sidebar .de VE .ie n 'mc .el \{\ .ev 2 .nf .ti 0 .mk ^t \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n' .sp -1 .fi .ev .\} .nr ^v 0 .. '\" # Special macro to handle page bottom: finish off current '\" # box/sidebar if in box/sidebar mode, then invoked standard '\" # page bottom macro. .de ^B .ev 2 'ti 0 'nf .mk ^t .if \\n(^b \{\ .\" Draw three-sided box if this is the box's first page, .\" draw two sides but no top otherwise. .ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .\} .if \\n(^v \{\ .nr ^x \\n(^tu+1v-\\n(^Yu \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c .\} .bp 'fi .ev .if \\n(^b \{\ .mk ^y .nr ^b 2 .\} .if \\n(^v \{\ .mk ^Y .\} .. '\" # DS - begin display .de DS .RS .nf .sp .. '\" # DE - end display .de DE .fi .RE .sp .. '\" # SO - start of list of standard options .de SO .SH "STANDARD OPTIONS" .LP .nf .ta 4c 8c 12c .ft B .. '\" # SE - end of list of standard options .de SE .fi .ft R .LP See the \\fBoptions\\fR manual entry for details on the standard options. .. '\" # OP - start of full description for a single option .de OP .LP .nf .ta 4c Command-Line Name: \\fB\\$1\\fR Database Name: \\fB\\$2\\fR Database Class: \\fB\\$3\\fR .fi .IP .. '\" # CS - begin code excerpt .de CS .RS .nf .ta .25i .5i .75i 1i .. '\" # CE - end code excerpt .de CE .fi .RE .. .de UL \\$1\l'|0\(ul'\\$2 .. .TH regexp n "" Tcl "Tcl Built-In Commands" .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME regexp \- Match a regular expression against a string .SH SYNOPSIS \fBregexp \fR?\fIswitches\fR? \fIexp string \fR?\fImatchVar\fR? ?\fIsubMatchVar subMatchVar ...\fR? .BE .SH DESCRIPTION .PP Determines whether the regular expression \fIexp\fR matches part or all of \fIstring\fR and returns 1 if it does, 0 if it doesn't. .LP If additional arguments are specified after \fIstring\fR then they are treated as the names of variables in which to return information about which part(s) of \fIstring\fR matched \fIexp\fR. \fIMatchVar\fR will be set to the range of \fIstring\fR that matched all of \fIexp\fR. The first \fIsubMatchVar\fR will contain the characters in \fIstring\fR that matched the leftmost parenthesized subexpression within \fIexp\fR, the next \fIsubMatchVar\fR will contain the characters that matched the next parenthesized subexpression to the right in \fIexp\fR, and so on. .LP If the initial arguments to \fBregexp\fR start with \fB\-\fR then .VS they are treated as switches. The following switches are currently supported: .TP 10 \fB\-nocase\fR Causes upper-case characters in \fIstring\fR to be treated as lower case during the matching process. .TP 10 \fB\-indices\fR Changes what is stored in the \fIsubMatchVar\fRs. Instead of storing the matching characters from \fBstring\fR, each variable will contain a list of two decimal strings giving the indices in \fIstring\fR of the first and last characters in the matching range of characters. .TP 10 \fB\-\|\-\fR Marks the end of switches. The argument following this one will be treated as \fIexp\fR even if it starts with a \fB\-\fR. .VE .LP If there are more \fIsubMatchVar\fR's than parenthesized subexpressions within \fIexp\fR, or if a particular subexpression in \fIexp\fR doesn't match the string (e.g. because it was in a portion of the expression that wasn't matched), then the corresponding \fIsubMatchVar\fR will be set to ``\fB\-1 \-1\fR'' if \fB\-indices\fR has been specified or to an empty string otherwise. .SH "REGULAR EXPRESSIONS" .PP Regular expressions are implemented using Henry Spencer's package (thanks, Henry!), and much of the description of regular expressions below is copied verbatim from his manual entry. .PP A regular expression is zero or more \fIbranches\fR, separated by ``|''. It matches anything that matches one of the branches. .PP A branch is zero or more \fIpieces\fR, concatenated. It matches a match for the first, followed by a match for the second, etc. .PP A piece is an \fIatom\fR possibly followed by ``*'', ``+'', or ``?''. An atom followed by ``*'' matches a sequence of 0 or more matches of the atom. An atom followed by ``+'' matches a sequence of 1 or more matches of the atom. An atom followed by ``?'' matches a match of the atom, or the null string. .PP An atom is a regular expression in parentheses (matching a match for the regular expression), a \fIrange\fR (see below), ``.'' (matching any single character), ``^'' (matching the null string at the beginning of the input string), ``$'' (matching the null string at the end of the input string), a ``\e'' followed by a single character (matching that character), or a single character with no other significance (matching that character). .PP A \fIrange\fR is a sequence of characters enclosed in ``[]''. It normally matches any single character from the sequence. If the sequence begins with ``^'', it matches any single character \fInot\fR from the rest of the sequence. If two characters in the sequence are separated by ``\-'', this is shorthand for the full list of ASCII characters between them (e.g. ``[0-9]'' matches any decimal digit). To include a literal ``]'' in the sequence, make it the first character (following a possible ``^''). To include a literal ``\-'', make it the first or last character. .SH "CHOOSING AMONG ALTERNATIVE MATCHES" .PP In general there may be more than one way to match a regular expression to an input string. For example, consider the command .CS \fBregexp (a*)b* aabaaabb x y\fR .CE Considering only the rules given so far, \fBx\fR and \fBy\fR could end up with the values \fBaabb\fR and \fBaa\fR, \fBaaab\fR and \fBaaa\fR, \fBab\fR and \fBa\fR, or any of several other combinations. To resolve this potential ambiguity \fBregexp\fR chooses among alternatives using the rule ``first then longest''. In other words, it considers the possible matches in order working from left to right across the input string and the pattern, and it attempts to match longer pieces of the input string before shorter ones. More specifically, the following rules apply in decreasing order of priority: .IP [1] If a regular expression could match two different parts of an input string then it will match the one that begins earliest. .IP [2] If a regular expression contains \fB|\fR operators then the leftmost matching sub-expression is chosen. .IP [3] In \fB*\fR, \fB+\fR, and \fB?\fR constructs, longer matches are chosen in preference to shorter ones. .IP [4] In sequences of expression components the components are considered from left to right. .LP In the example from above, \fB(a*)b*\fR matches \fBaab\fR: the \fB(a*)\fR portion of the pattern is matched first and it consumes the leading \fBaa\fR; then the \fBb*\fR portion of the pattern consumes the next \fBb\fR. Or, consider the following example: .CS \fBregexp (ab|a)(b*)c abc x y z\fR .CE After this command \fBx\fR will be \fBabc\fR, \fBy\fR will be \fBab\fR, and \fBz\fR will be an empty string. Rule 4 specifies that \fB(ab|a)\fR gets first shot at the input string and Rule 2 specifies that the \fBab\fR sub-expression is checked before the \fBa\fR sub-expression. Thus the \fBb\fR has already been claimed before the \fB(b*)\fR component is checked and \fB(b*)\fR must match an empty string. .SH KEYWORDS match, regular expression, string