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Diffstat (limited to 'doc/switch.n')
| -rw-r--r-- | doc/switch.n | 141 |
1 files changed, 110 insertions, 31 deletions
diff --git a/doc/switch.n b/doc/switch.n index 503a5ba..6e27f56 100644 --- a/doc/switch.n +++ b/doc/switch.n @@ -5,10 +5,8 @@ '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" -'\" RCS: @(#) $Id: switch.n,v 1.2 1998/09/14 18:39:55 stanton Exp $ -'\" +.TH switch n 8.5 Tcl "Tcl Built-In Commands" .so man.macros -.TH switch n 7.0 Tcl "Tcl Built-In Commands" .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME @@ -18,7 +16,6 @@ switch \- Evaluate one of several scripts, depending on a given value .sp \fBswitch \fR?\fIoptions\fR?\fI string \fR{\fIpattern body \fR?\fIpattern body \fR...?} .BE - .SH DESCRIPTION .PP The \fBswitch\fR command matches its \fIstring\fR argument against each of @@ -33,25 +30,68 @@ matches \fIstring\fR and no default is given, then the \fBswitch\fR command returns an empty string. .PP If the initial arguments to \fBswitch\fR start with \fB\-\fR then -they are treated as options. The following options are -currently supported: +they are treated as options +unless there are exactly two arguments to \fBswitch\fR (in which case the +first must the \fIstring\fR and the second must be the +\fIpattern\fR/\fIbody\fR list). +The following options are currently supported: .TP 10 \fB\-exact\fR +. Use exact matching when comparing \fIstring\fR to a pattern. This is the default. .TP 10 \fB\-glob\fR +. When matching \fIstring\fR to the patterns, use glob-style matching (i.e. the same as implemented by the \fBstring match\fR command). .TP 10 \fB\-regexp\fR +. When matching \fIstring\fR to the patterns, use regular expression matching -(i.e. the same as implemented by the \fBregexp\fR command). +(as described in the \fBre_syntax\fR reference page). +.TP 10 +\fB\-nocase\fR +. +Causes comparisons to be handled in a case-insensitive manner. +.TP 10 +\fB\-matchvar\fR \fIvarName\fR +. +This option (only legal when \fB\-regexp\fR is also specified) +specifies the name of a variable into which the list of matches +found by the regular expression engine will be written. The first +element of the list written will be the overall substring of the input +string (i.e. the \fIstring\fR argument to \fBswitch\fR) matched, the +second element of the list will be the substring matched by the first +capturing parenthesis in the regular expression that matched, and so +on. When a \fBdefault\fR branch is taken, the variable will have the +empty list written to it. This option may be specified at the same +time as the \fB\-indexvar\fR option. +.TP 10 +\fB\-indexvar\fR \fIvarName\fR +. +This option (only legal when \fB\-regexp\fR is also specified) +specifies the name of a variable into which the list of indices +referring to matching substrings +found by the regular expression engine will be written. The first +element of the list written will be a two-element list specifying the +index of the start and index of the first character after the end of +the overall substring of the input +string (i.e. the \fIstring\fR argument to \fBswitch\fR) matched, in a +similar way to the \fB\-indices\fR option to the \fBregexp\fR can +obtain. Similarly, the second element of the list refers to the first +capturing parenthesis in the regular expression that matched, and so +on. When a \fBdefault\fR branch is taken, the variable will have the +empty list written to it. This option may be specified at the same +time as the \fB\-matchvar\fR option. .TP 10 \fB\-\|\-\fR +. Marks the end of options. The argument following this one will be treated as \fIstring\fR even if it starts with a \fB\-\fR. +This is not required when the matching patterns and bodies are grouped +together in a single argument. .PP Two syntaxes are provided for the \fIpattern\fR and \fIbody\fR arguments. The first uses a separate argument for each of the patterns and commands; @@ -68,40 +108,79 @@ no command or variable substitutions are performed on them; this makes the behavior of the second form different than the first form in some cases. .PP -If a \fIbody\fR is specified as ``\fB\-\fR'' it means that the \fIbody\fR +If a \fIbody\fR is specified as +.QW \fB\-\fR +it means that the \fIbody\fR for the next pattern should also be used as the body for this -pattern (if the next pattern also has a body of ``\fB\-\fR'' +pattern (if the next pattern also has a body of +.QW \fB\-\fR then the body after that is used, and so on). This feature makes it possible to share a single \fIbody\fR among several patterns. .PP -Below are some examples of \fBswitch\fR commands: +Beware of how you place comments in \fBswitch\fR commands. Comments +should only be placed \fBinside\fR the execution body of one of the +patterns, and not intermingled with the patterns. +.SH "EXAMPLES" +.PP +The \fBswitch\fR command can match against variables and not just +literals, as shown here (the result is \fI2\fR): +.PP +.CS +set foo "abc" +\fBswitch\fR abc a \- b {expr {1}} $foo {expr {2}} default {expr {3}} +.CE +.PP +Using glob matching and the fall-through body is an alternative to +writing regular expressions with alternations, as can be seen here +(this returns \fI1\fR): +.PP .CS -\fBswitch\0abc\0a\0\-\0b\0{format 1}\0abc\0{format 2}\0default\0{format 3}\fR +\fBswitch\fR \-glob aaab { + a*b \- + b {expr {1}} + a* {expr {2}} + default {expr {3}} +} .CE -will return \fB2\fR, +.PP +Whenever nothing matches, the \fBdefault\fR clause (which must be +last) is taken. This example has a result of \fI3\fR: +.PP .CS -\fBswitch\0\-regexp\0aaab { - ^a.*b$\0\- - b\0{format 1} - a*\0{format 2} - default\0{format 3} -}\fR +\fBswitch\fR xyz { + a \- + b { + # Correct Comment Placement + expr {1} + } + c { + expr {2} + } + default { + expr {3} + } +} .CE -will return \fB1\fR, and +.PP +When matching against regular expressions, information about what +exactly matched is easily obtained using the \fB\-matchvar\fR option: +.PP .CS -\fBswitch\0xyz { - a - \- - b - {format 1} - a* - {format 2} - default - {format 3} -}\fR +\fBswitch\fR \-regexp \-matchvar foo \-\- $bar { + a(b*)c { + puts "Found [string length [lindex $foo 1]] 'b's" + } + d(e*)f(g*)h { + puts "Found [string length [lindex $foo 1]] 'e's and\e + [string length [lindex $foo 2]] 'g's" + } +} .CE -will return \fB3\fR. - +.SH "SEE ALSO" +for(n), if(n), regexp(n) .SH KEYWORDS switch, match, regular expression +.\" Local Variables: +.\" mode: nroff +.\" End: |