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

You want to run the make process in a pipeline and use the event loop and fileevent to monitor its progress (see http://wiki.tcl.tk/880)

proc handle_make_output {chan} {
    # The channel is readable; try to read it.
    set status [catch { gets $chan line } result]
    if { $status != 0 } {
        # Error on the channel
        puts "error reading $chan: $result"
        set ::DONE 2
    } elseif { $result >= 0 } {
        # Successfully read the channel
        puts "got: $line"
    } elseif { [chan eof $chan] } {
        # End of file on the channel
        puts "end of file"
        set ::DONE 1
    } elseif { [chan blocked $chan] } {
        # Read blocked.  Just return
    } else {
        # Something else
        puts "can't happen"
        set ::DONE 3
    }
}

set chan [open "|make" r]
chan configure $chan -blocking false
chan event $chan readable [list handle_make_output $chan]
vwait ::DONE
close $chan

I'm not certain about the use of vwait within Tk's event loop. Perhaps an expert will help me out here.