#!/bin/ksh
# $Header: /afs/northstar/ufac/richard/projects/mcasey/run-with-timeout,v 1.5 2008/10/22 16:51:00 richard Exp $
#
# Run a command, but kill it if it has not returned after $timeout seconds
#
# Richard Brittain, 2008/07/05
#
# 1.1: tested on OSX 10.4 with ksh
#
# Make sure backgrounded processes are not auto-niced.
set +o bgnice

timeout=$1; shift

# signal handler to trap ALRM
function timeout_handler
{
   # Other logging possible here.  
   echo "timeout after $timeout s: \"$command $args\": killed" >&2
   # Kill the process which didn't complete as expected
   # If $proc isn't set, we got called too soon.
   [[ -n "$proc" ]] && kill -s TERM $proc
   # Set an exit status to be returned to indicate timeout
   estatus=127
}

# Get the command and arguments to be run
command=$1; shift
args="$@"

# Set trap on SIGALRM
trap timeout_handler ALRM

# Now start the alarm timer
# Arrange to interrupt ourselves after some timeout
# $pid is PID of this shell
pid=$$
(
   # Sleep for $timeout seconds.  If we haven't been killed, send a SIGALRM to our caller
   sleep $timeout
   kill -s ALRM $pid
) &
# $alarm is the PID of the alarm subshell itself
alarm=$!

# Run the command in background and get the PID in $proc so we can kill it if needed
# Using 'eval' allows us to process shell redirection and other metacharacters, but breaks
# quoting for any argument with embedded spaces.  
# Don't allow shell metacharacters as actual arguments.  This probably won't work if the command is a pipeline
## eval "$command" "$args" \&
$command "$@" &
proc=$!
# Now wait for the command to complete.  Generally this is what will be interrupted if it times out
wait $proc
pstatus=$?
# The process exit status is captured in $pstatus, if it completed.
# Kill the alarm process, if it is still running (don't bother testing)
kill -s TERM $alarm 2>/dev/null
# echo "Exiting with status ${estatus:-$pstatus}" >&2
exit ${estatus:-$pstatus}