Description: Execute script repeatedly as long as a condition is met
Syntax: while test body
Argument: test, body of commands
Returns:
See Also: if, foreach, , for, SCRLOOP
Examples:
#example 1
while {$i < $rcptlen} {
set e [expr {$i+$cur(batchsize)-1}]
if {$e >= $rcptlen} {
set e [expr {$rcptlen-1}]
}
#example 2 counts 0 to 9
set x 0
while {$x<10} {
SETVAL tagx=$x
incr x
}
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 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 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 variables will be visible.