while(n) - phpMan

while(n)                              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 interpreter.  Once body has been executed
       then test is evaluated again, and the process repeats until eventually test evaluates to a
       false  boolean value.  Continue commands may be executed inside body to terminate the cur-
       rent iteration of the loop, and break commands may be executed inside body to cause  imme-
       diate 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 expression.  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 vari-
       ables 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
              }

EXAMPLE
       Read lines from a channel until we get to the end of the stream, and print them out with a
       line-number prepended:
              set lineCount 0
              while {[gets $chan line] >= 0} {
                  puts "[incr lineCount]: $line"
              }


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


KEYWORDS
       boolean value, loop, test, while



Tcl                                                                                      while(n)

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