#!/usr/bin/ruby -w
# $Id: impatient,v 1.4 2006/11/24 14:34:16 mark Exp $

if ARGV.length < 3

  print <<EOF
Usage: impatient <timeout-seconds> <return-value-on-timeout> <command>

   Returns <command>'s return code if it completed in
   <timeout-seconds>, or <return-value-on-timeout> otherwise.
EOF

  exit

end

timeoutSeconds, timeoutReturnValue, *command = ARGV

childpid = nil

# Add a handler for SIGCHLD:

trap("CLD") {

  endedpid = Process.wait

  if endedpid == childpid
    exit $?
  else
    # Otherwise some other child process exited, do nothing...
  end
}

# We fork, and run command in the child.  After sleeping for timeout
# seconds in the parent, we kill the child.  The parent will have
# already exited via the handler for SIGCHLD if the command has
# completed...

childpid = fork

if childpid

  # In the parent..

  begin
    sleep timeoutSeconds.to_i
  rescue
    print "Couldn't sleep for #{timeoutSeconds} seconds...\n"
    exit
  end

  Process.kill( "SIGTERM", -childpid )

  exit timeoutReturnValue.to_i

else 

  # In the child...

  # We want to be able kill all the child processes as well, so set
  # the process group to this PID:

  Process.setpgrp
  exec( *command )

end