source: vendor/bash/3.1/examples/scripts/timeout

#Newsgroups: comp.unix.admin,comp.unix.solaris,comp.unix.shell
#From: gwc@root.co.uk (Geoff Clare)
#Subject: Re: timeout -t <sec> <unix command> (Re: How to give rsh a shorter timeout?)
#Message-ID: <EoBxrs.223@root.co.uk>
#Date: Fri, 13 Feb 1998 18:23:52 GMT

#
# Conversion to bash v2 syntax done by Chet Ramey <chet@po.cwru.edu
# UNTESTED
#

prog=${0##*/}
usage="usage: $prog [-signal] [timeout] [:interval] [+delay] [--] <command>"

SIG=-TERM       # default signal sent to the process when the timer expires
timeout=60      # default timeout
interval=15     # default interval between checks if the process is still alive
delay=2         # default delay between posting the given signal and
                # destroying the process (kill -KILL)

while :
do
        case $1 in
        --)     shift; break ;;
        -*)     SIG=$1 ;;
        [0-9]*) timeout=$1 ;;
        :*)     EXPR='..\(.*\)' ; interval=`expr x"$1" : "$EXPR"` ;;
        +*)     EXPR='..\(.*\)' ; delay=`expr x"$1" : "$EXPR"` ;;
        *)      break ;;
        esac
        shift
done

case $# in
0)      echo "$prog: $usage" >&2 ; exit 2 ;;
esac

(
        for t in $timeout $delay
        do
                while (( $t > $interval ))
                do
                        sleep $interval
                        kill -0 $$ || exit
                        t=$(( $t - $interval ))
                done
                sleep $t
                kill $SIG $$ && kill -0 $$ || exit
                SIG=-KILL
        done
) 2> /dev/null &

exec "$@"