Advanced Search
Mail us
Home    Manuel    Links    Faq     Some examples tcl/tk codes     Man of Bwidget with screenshot     Man of blt with screenshot


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


while test body


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. 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


boolean value, loop, test, while
Copyright © 1993 The Regents of the University of California.
Copyright © 1994-1997 Sun Microsystems, Inc.
Copyright © 1995-1997 Roger E. Critchlow Jr.
Erreur (1146) : Table 'tcltk.tcltksamplemancode' doesn't exist

Add a code sample :

Please enter your name and your email ( the I could thank's you ). Don't enter html code in the text area If you have any problem email me at this adress
 Your name    
 Your email    
 Your example