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



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NAME
       if - Execute scripts conditionally

SYNOPSIS
       if expr1 ?then? body1 elseif expr2 ?then? body2 elseif ... ?else? ?bodyN?
____________________________________________________________________________________________________________


DESCRIPTION
       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 interpreter.  Otherwise expr2 is evaluated as  an  expres-sion expression
       sion  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 com-mand command
       mand  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 command 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.

EXAMPLES
       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"
              }


SEE ALSO
       expr(n), for(n), foreach(n)


KEYWORDS
       boolean, conditional, else, false, if, true



Tcl                                                                                                    if(n)