Detect end of TCL background process in a TCL script

Question

I\'m working on a program the uses an EXEC command to run a make file. This can take a long time so I want to put it in the background so the GUI doesn\'t lock up. However I

Answer 1

As @glenn-jackman pointed out, the use of fileevent is preferred (because it should work everywhere).

proc handle_bgexec {callback chan} {
    append ::bgexec_data($chan) [read $chan]
    if {[eof $chan]} {
        # end of file, call the callback
        {*}$callback $::bgexec_data($chan)
        unset ::bgexec_data($chan)
    }
}

proc bgexec {callback args} {
    set chan [open "| $args" r]
    fconfigure $chan -blocking false
    fileevent $chan readable [list handle_bgexec $callback $chan]
    return
}

Invoke this as bgexec job_done cmd /c start /wait cmd /c make all-all. job_done gets called with the output of the command after it finishes.

It is also possible to use threads for this things, but this requires a threaded tcl build (which is now default for all platforms AFAIK, but older versions of Tcl esp. under unix don't build a threaded Tcl by default.) and the Thread package (which is included by default). An approach to use it with Threads would be:

thread::create "[list exec cmd /c start /wait cmd /c make all-all];[list thread::send [thread::id] {callback code}];thread::exit"

If you need to call this on a regular basis it might be worth to use only one worker thread instead of creating a new one for each job.

Edit: Add /wait as parameter for start the keep the first cmd running.

cmd /c start /wait cmd /c make all-all