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switch(n)		     Tcl Built-In Commands		     switch(n)

______________________________________________________________________________

NAME
       switch - Evaluate one of several scripts, depending on a given value

SYNOPSIS
       switch ?options? string pattern body ?pattern body ...?

       switch ?options? string {pattern body ?pattern body ...?}
_________________________________________________________________

DESCRIPTION
       The switch command matches its string argument against each of the pat‐
       tern arguments in order.	 As soon as it finds a	pattern	 that  matches
       string  it  evaluates  the following body argument by passing it recur‐
       sively to the Tcl interpreter and returns the result  of	 that  evalua‐
       tion.   If  the	last  pattern argument is default then it matches any‐
       thing.  If no pattern argument matches string and no default is	given,
       then the switch command returns an empty string.

       If  the	initial arguments to switch start with - then they are treated
       as options.  The following options are currently supported:

       -exact	 Use exact matching when comparing string to a pattern.	  This
		 is the default.

       -glob	 When matching string to the patterns, use glob-style matching
		 (i.e. the same as implemented by the string match command).

       -regexp	 When matching string to the patterns, use regular  expression
		 matching  (i.e.  the  same  as implemented by the regexp com‐
		 mand).

       --	 Marks the end of options.  The argument  following  this  one
		 will be treated as string even if it starts with a -.

       Two  syntaxes  are  provided  for  the pattern and body arguments.  The
       first uses a separate argument for each of the patterns	and  commands;
       this  form  is  convenient  if substitutions are desired on some of the
       patterns or commands.  The second form places all of the	 patterns  and
       commands together into a single argument; the argument must have proper
       list structure, with the elements of the list being  the	 patterns  and
       commands.  The second form makes it easy to construct multi-line switch
       commands, since the braces around the whole list make it unnecessary to
       include	a  backslash at the end of each line.  Since the pattern argu‐
       ments are in braces in the second form, no command or variable  substi‐
       tutions	are  performed on them;	 this makes the behavior of the second
       form different than the first form in some cases.

       If a body is specified as ``-'' it means that the  body	for  the  next
       pattern	should	also be used as the body for this pattern (if the next
       pattern also has a body of ``-'' then the body after that is used,  and
       so  on).	  This	feature makes it possible to share a single body among
       several patterns.

       Below are some examples of switch commands:
	      switch abc a - b {format 1} abc {format 2} default {format 3}
       will return 2,
	      switch -regexp aaab {
		^a.*b$ -
		b {format 1}
		a* {format 2}
		default {format 3}
	      }
       will return 1, and
	      switch xyz {
		a
		   -
		b
		   {format 1}
		a*
		   {format 2}
		default
		   {format 3}
	      }
       will return 3.

KEYWORDS
       switch, match, regular expression

Tcl				      7.0			     switch(n)
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