-#!/bin/sh
-
-# Execute a command with a timeout
-
-# License: LGPLv2
-# Author:
-# http://www.pixelbeat.org/
-# Notes:
-# Note there is a timeout command packaged with coreutils since v7.0
-# If the timeout occurs the exit status is 124.
-# There is an asynchronous (and buggy) equivalent of this
-# script packaged with bash (under /usr/share/doc/ in my distro),
-# which I only noticed after writing this.
-# I noticed later again that there is a C equivalent of this packaged
-# with satan by Wietse Venema, and copied to forensics by Dan Farmer.
-# Changes:
-# V1.0, Nov 3 2006, Initial release
-# V1.1, Nov 20 2007, Brad Greenlee <brad@footle.org>
-# Make more portable by using the 'CHLD'
-# signal spec rather than 17.
-# V1.3, Oct 29 2009, Ján Sáreník <jasan@x31.com>
-# Even though this runs under dash,ksh etc.
-# it doesn't actually timeout. So enforce bash for now.
-# Also change exit on timeout from 128 to 124
-# to match coreutils.
-# V2.0, Oct 30 2009, Ján Sáreník <jasan@x31.com>
-# Rewritten to cover compatibility with other
-# Bourne shell implementations (pdksh, dash)
-
-if [ "$#" -lt "2" ]; then
- echo "Usage: `basename $0` timeout_in_seconds command" >&2
- echo "Example: `basename $0` 2 sleep 3 || echo timeout" >&2
+#!/bin/bash
+#
+# The Bash shell script executes a command with a time-out.
+# Upon time-out expiration SIGTERM (15) is sent to the process. If the signal
+# is blocked, then the subsequent SIGKILL (9) terminates it.
+#
+# Based on the Bash documentation example.
+
+# Hello Chet,
+# please find attached a "little easier" :-) to comprehend
+# time-out example. If you find it suitable, feel free to include
+# anywhere: the very same logic as in the original examples/scripts, a
+# little more transparent implementation to my taste.
+#
+# Dmitry V Golovashkin <Dmitry.Golovashkin@sas.com>
+
+scriptName="${0##*/}"
+
+declare -i DEFAULT_TIMEOUT=9
+declare -i DEFAULT_INTERVAL=1
+declare -i DEFAULT_DELAY=1
+
+# Timeout.
+declare -i timeout=DEFAULT_TIMEOUT
+# Interval between checks if the process is still alive.
+declare -i interval=DEFAULT_INTERVAL
+# Delay between posting the SIGTERM signal and destroying the process by SIGKILL.
+declare -i delay=DEFAULT_DELAY
+
+function printUsage() {
+ cat <<EOF
+
+Synopsis
+ $scriptName [-t timeout] [-i interval] [-d delay] command
+ Execute a command with a time-out.
+ Upon time-out expiration SIGTERM (15) is sent to the process. If SIGTERM
+ signal is blocked, then the subsequent SIGKILL (9) terminates it.
+
+ -t timeout
+ Number of seconds to wait for command completion.
+ Default value: $DEFAULT_TIMEOUT seconds.
+
+ -i interval
+ Interval between checks if the process is still alive.
+ Positive integer, default value: $DEFAULT_INTERVAL seconds.
+
+ -d delay
+ Delay between posting the SIGTERM signal and destroying the
+ process by SIGKILL. Default value: $DEFAULT_DELAY seconds.
+
+As of today, Bash does not support floating point arithmetic (sleep does),
+therefore all delay/time values must be integers.
+EOF
+}
+
+# Options.
+while getopts ":t:i:d:" option; do
+ case "$option" in
+ t) timeout=$OPTARG ;;
+ i) interval=$OPTARG ;;
+ d) delay=$OPTARG ;;
+ *) printUsage; exit 1 ;;
+ esac
+done
+shift $((OPTIND - 1))
+
+# $# should be at least 1 (the command to execute), however it may be strictly
+# greater than 1 if the command itself has options.
+if (($# == 0 || interval <= 0)); then
+ printUsage
exit 1
fi
-cleanup()
-{
- trap - ALRM #reset handler to default
- kill -ALRM $a 2>/dev/null #stop timer subshell if running
- kill $! 2>/dev/null && #kill last job
- exit 124 #exit with 124 if it was running
-}
+# kill -0 pid Exit code indicates if a signal may be sent to $pid process.
+(
+ ((t = timeout))
-watchit()
-{
- trap "cleanup" ALRM
- sleep $1& wait
- kill -ALRM $$
-}
+ while ((t > 0)); do
+ sleep $interval
+ kill -0 $$ || exit 0
+ ((t -= interval))
+ done
-watchit $1& a=$! #start the timeout
-shift #first param was timeout for sleep
-trap "cleanup" ALRM INT #cleanup after timeout
-"$@"& wait $!; RET=$? #start the job wait for it and save its return value
-kill -ALRM $a #send ALRM signal to watchit
-wait $a #wait for watchit to finish cleanup
-exit $RET #return the value
+ # Be nice, post SIGTERM first.
+ # The 'exit 0' below will be executed if any preceeding command fails.
+ kill -s SIGTERM $$ && kill -0 $$ || exit 0
+ sleep $delay
+ kill -s SIGKILL $$
+) 2> /dev/null &
+exec "$@"
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