GSP
Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Support
Contact Us
Online Help
Handbooks
Domain Status
Man Pages

FAQ
Virtual Servers
Pricing
Billing
Technical

Network
Facilities
Connectivity
Topology Map

Miscellaneous
Server Agreement
Year 2038
Credits
 

USA Flag

 

 

Man Pages


Manual Reference Pages  -  FOR (n)

NAME

for - ’For’ loop

CONTENTS

Synopsis
Description
Examples
Keywords

SYNOPSIS

for start test next body

   








\L’|0u-1v’\l’75u+3n_’\L’0u+1v-0u’\l’|0u-1.5n_’



\L’|0u-1v’\L’0u+1v-0u’\l’|0u-1.5n_’





DESCRIPTION

For is a looping command, similar in structure to the C for statement. The start, next, and body arguments must be Tcl command strings, and test is an expression string. The for command first invokes the Tcl interpreter to execute start. Then it repeatedly evaluates test as an expression; if the result is non-zero it invokes the Tcl interpreter on body, then invokes the Tcl interpreter on next, then repeats the loop. The command terminates when test evaluates to 0. If a continue command is invoked within body then any remaining commands in the current execution of body are skipped; processing continues by invoking the Tcl interpreter on next, then evaluating test, and so on. If a break command is invoked within body or next, then the for command will return immediately. The operation of break and continue are similar to the corresponding statements in C. For returns an empty string.

Note: test should almost always be enclosed in braces. If not, variable substitutions will be made before the for 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. See below for an example:

EXAMPLES

Print a line for each of the integers from 0 to 10:

for {set x 0} {$x<10} {incr x} {
   puts "x is $x"
}


Either loop infinitely or not at all because the expression being evaluated is actually the constant, or even generate an error! The actual behaviour will depend on whether the variable x exists before the for command is run and whether its value is a value that is less than or greater than/equal to ten, and this is because the expression will be substituted before the for command is executed.


for {set x 0} $x<10 {incr x} {
   puts "x is $x"
}


Print out the powers of two from 1 to 1024:


for {set x 1} {$x<=1024} {set x [expr {$x * 2}]} {
   puts "x is $x"
}


SEE ALSO

break, continue, foreach, while

KEYWORDS

for, iteration, looping
Search for    or go to Top of page |  Section n |  Main Index


Tcl FOR (n)

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.