run command continuously in background using tcl - linux

Question

I am using tcl/expect for testing an ethernet switch. I want to run some test tool repeatedly every 2 seconds and in background. The output can be ignored.
That is I want to do the following:
Have one block of code which repeats the following over and over until stopped from the other block of code:
exec { $myCommand }
sleep $sleepDuration
$myCommand can be either a list or a string, whatever is more convenient. $sleepDuration is a number.
In the other block of code I will do normal operations, including spawning processes and talking to them or interacting with already existing connections.
Is that possible with tcl? I am running on Debian Linux 6 in VMWare. The code doesn't need to be portable to other plattforms.
I have tried using watch but I am not sure how to do the following:
exec {watch $myCommand}
switch to an already connected process
interact with it
switch to watch
send "\x03"

Answer 1

In the simplest case, where the command is quickly running, you use the every pattern:
proc every {delay script} {
uplevel #0 $script
after $delay [info level 0]
}
every 2000 {exec $yourCommand $yourArgument &}
Then, as long as you're servicing the Tcl event loop, the command will be run every 2 seconds (== 2000 milliseconds).