tcl7.6 User Commands - if






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 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
     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.



KEYWORDS

     boolean, conditional, else, false, if, true