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OpenDarwin 7.2.1 - man page for switch (opendarwin section n)

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 pattern arguments in
       order.  As soon as it finds a pattern that matches string it evaluates the following  body
       argument  by  passing it recursively to the Tcl interpreter and returns the result of that
       evaluation.  If the last pattern argument is default then it matches anything.  If no pat-
       tern  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  pat-
       terns  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  pat-
       tern  arguments are in braces in the second form, 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.

       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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