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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 (as described in the re_syntax reference page).

       --	 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.

       Beware  of  how you place comments in switch commands.  Comments should
       only be placed inside the execution body of one of  the	patterns,  and
       not intermingled with the 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
		   {
		   # Correct Comment Placement
		   format 1
		}
		a*
		   {format 2}
		default
		   {format 3}
	      }
       will return 3.

SEE ALSO
       for(n), if(n), regexp(n)

KEYWORDS
       switch, match, regular expression

Tcl				      7.0			     switch(n)
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