Tcl Built-In Commands                                    while(n)

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NAME
     while - Execute script repeatedly as long as a condition  is
     met

SYNOPSIS
     while test body
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DESCRIPTION
     The while command evaluates test as an  expression  (in  the
     same  way  that  expr evaluates its argument).  The value of
     the expression must a proper boolean value; if it is a  true
     value  then body is executed by passing it to the Tcl inter-
     preter.  Once body has been executed then test is  evaluated
     again,  and the process repeats until eventually test evalu-
     ates to a false boolean value.   Continue  commands  may  be
     executed  inside  body to terminate the current iteration of
     the loop, and break commands may be executed inside body  to
     cause immediate termination of the while command.  The while
     command always returns an empty string.

     Note: test should almost always be enclosed in  braces.   If
     not,  variable  substitutions  will be made before the while
     command starts executing, which means that variable  changes
     made  by the loop body will not be considered in the expres-
     sion.  This is likely to result in  an  infinite  loop.   If
     test  is  enclosed  in  braces,  variable  substitutions are
     delayed until the expression is evaluated (before each  loop
     iteration),  so  changes  in  the variables will be visible.
     For an example, try the following script  with  and  without
     the braces around $x<10:
          set x 0
          while {$x<10} {
            puts "x is $x"
            incr x
          }

SEE ALSO
     break(n), continue(n), for(n), foreach(n)

KEYWORDS
     boolean value, loop, test, while

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