for(n) Tcl Built-In Commands for(n) 







for - 'For' loop








for start test next body












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:








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"
}












break, continue, foreach, while










for, iteration, looping







  

    
    Tcl