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


       if - Execute scripts conditionally

       if  expr1 ?then?	body1 elseif expr2 ?then? body2	elseif ... ?else? ?bo-

       The if command evaluates	expr1 as an expression (in the same  way  that
       expr  evaluates	its  argument).	 The value of the expression must be a
       boolean (a numeric value, where 0 is false and anything is true,	 or  a
       string  value  such as true or yes for true and false or	no for false);
       if it is	true then body1	is executed by passing it to  the  Tcl	inter-
       preter.	 Otherwise  expr2  is  evaluated as an expression and if it is
       true then body2 is executed, and	so on.	If  none  of  the  expressions
       evaluates  to true then bodyN is	executed.  The then and	else arguments
       are optional "noise words" to make the command easier to	 read.	 There
       may be any number of elseif clauses, including zero.  BodyN may also be
       omitted as long as else is omitted too.	The return value from the com-
       mand  is	 the  result of	the body script	that was executed, or an empty
       string if none of the expressions was non-zero and there	was no bodyN.

       A simple	conditional:

	      if {$vbl == 1} { puts "vbl is one" }

       With an else-clause:

	      if {$vbl == 1} {
		  puts "vbl is one"
	      }	else {
		  puts "vbl is not one"

       With an elseif-clause too:

	      if {$vbl == 1} {
		  puts "vbl is one"
	      }	elseif {$vbl ==	2} {
		  puts "vbl is two"
	      }	else {
		  puts "vbl is not one or two"

       Remember, expressions can be multi-line,	but in that case it can	 be  a
       good idea to use	the optional then keyword for clarity:

	      if {
		  $vbl == 1
		  || $vbl == 2
		  || $vbl == 3
	      }	then {
		  puts "vbl is one, two	or three"

       expr(n),	for(n),	foreach(n)

       boolean,	conditional, else, false, if, true

Tcl									 if(n)


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