Appending to a string

Creating a string in Tcl using the set command is the starting point for all string commands. This will be the first command for most, if not all of the following recipes. As we have seen previously, entering a set variable value on the command line does this. However, to fully implement strings within a Tcl script, we need to interact with these strings from time to time, for example, with an open channel to a file or HTTP pipe. To accomplish this, we will need to read from the channel and append to the original string.

To accomplish appending to a string, Tcl provides the append command. The append command is as follows:

append variable value value value…

How to do it…

In the following example, we will create a string of comma-delimited numbers using the for control construct. Return values from the commands are provided for clarity. Enter the following command:

% set var 0
0
% for {set x 1} {$x<=10}{$x<=10} {incr x} {
append var , $x
}
%puts $var
0,1,2,3,4,5...