Event-driven exec

constructor {job_ commandline} {
    set job $job_
    pipe errout errin
    #pipe in_out in_in
    pipe out_out out_in
    fconfigure $errout -blocking false
    fileevent $errout readable [mymethod read_err]

    dput "RUNNING '$commandline'"
    set in_in [open "| >@ $out_in 2>@ $errin $commandline" w]
    set pids [pid $in_in]
    dput "PIDS '$pids'"

    foreach pid $pids { set pid_handlers($pid) $self }

    fconfigure $out_out -blocking false
    fileevent $out_out readable [mymethod read_out]
    close $errin
    close $out_in
    #close $in_out

    set comstat running
}