108 lines
3.5 KiB
Plaintext
108 lines
3.5 KiB
Plaintext
'\"
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'\" Copyright (c) 1993 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" SCCS: @(#) switch.n 1.8 96/03/25 20:24:31
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'\"
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.so man.macros
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.TH switch n 7.0 Tcl "Tcl Built-In Commands"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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switch \- Evaluate one of several scripts, depending on a given value
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.SH SYNOPSIS
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\fBswitch\fI \fR?\fIoptions\fR?\fI string \fIpattern body \fR?\fIpattern body \fR...?
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.sp
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\fBswitch\fI \fR?\fIoptions\fR?\fI string \fR{\fIpattern body \fR?\fIpattern body \fR...?}
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.BE
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.SH DESCRIPTION
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.PP
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The \fBswitch\fR command matches its \fIstring\fR argument against each of
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the \fIpattern\fR arguments in order.
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As soon as it finds a \fIpattern\fR that matches \fIstring\fR it
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evaluates the following \fIbody\fR argument by passing it recursively
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to the Tcl interpreter and returns the result of that evaluation.
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If the last \fIpattern\fR argument is \fBdefault\fR then it matches
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anything.
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If no \fIpattern\fR argument
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matches \fIstring\fR and no default is given, then the \fBswitch\fR
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command returns an empty string.
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.PP
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If the initial arguments to \fBswitch\fR start with \fB\-\fR then
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they are treated as options. The following options are
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currently supported:
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.TP 10
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\fB\-exact\fR
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Use exact matching when comparing \fIstring\fR to a pattern. This
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is the default.
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.TP 10
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\fB\-glob\fR
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When matching \fIstring\fR to the patterns, use glob-style matching
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(i.e. the same as implemented by the \fBstring match\fR command).
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.TP 10
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\fB\-regexp\fR
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When matching \fIstring\fR to the patterns, use regular
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expression matching
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(i.e. the same as implemented by the \fBregexp\fR command).
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.TP 10
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\fB\-\|\-\fR
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Marks the end of options. The argument following this one will
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be treated as \fIstring\fR even if it starts with a \fB\-\fR.
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.PP
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Two syntaxes are provided for the \fIpattern\fR and \fIbody\fR arguments.
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The first uses a separate argument for each of the patterns and commands;
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this form is convenient if substitutions are desired on some of the
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patterns or commands.
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The second form places all of the patterns and commands together into
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a single argument; the argument must have proper list structure, with
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the elements of the list being the patterns and commands.
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The second form makes it easy to construct multi-line switch commands,
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since the braces around the whole list make it unnecessary to include a
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backslash at the end of each line.
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Since the \fIpattern\fR arguments are in braces in the second form,
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no command or variable substitutions are performed on them; this makes
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the behavior of the second form different than the first form in some
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cases.
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.PP
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If a \fIbody\fR is specified as ``\fB\-\fR'' it means that the \fIbody\fR
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for the next pattern should also be used as the body for this
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pattern (if the next pattern also has a body of ``\fB\-\fR''
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then the body after that is used, and so on).
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This feature makes it possible to share a single \fIbody\fR among
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several patterns.
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.PP
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Below are some examples of \fBswitch\fR commands:
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.CS
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\fBswitch\0abc\0a\0\-\0b\0{format 1}\0abc\0{format 2}\0default\0{format 3}\fR
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.CE
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will return \fB2\fR,
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.CS
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\fBswitch\0\-regexp\0aaab {
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^a.*b$\0\-
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b\0{format 1}
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a*\0{format 2}
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default\0{format 3}
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}\fR
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.CE
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will return \fB1\fR, and
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.CS
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\fBswitch\0xyz {
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a
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\-
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b
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{format 1}
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a*
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{format 2}
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default
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{format 3}
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}\fR
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.CE
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will return \fB3\fR.
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.SH KEYWORDS
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switch, match, regular expression
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