Timeout some commands

tools/timeout.sh

@@ -0,0 +1,91 @@
+#!/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=20
+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
+
+# kill -0 pid   Exit code indicates if a signal may be sent to $pid process.
+(
+    ((t = timeout))
+
+    while ((t > 0)); do
+        sleep $interval
+        kill -0 $$ || exit 0
+        ((t -= interval))
+    done
+
+    # Be nice, post SIGTERM first.
+    # The 'exit 0' below will be executed if any preceeding command fails.
+    kill -s SIGTERM $$ && kill -0 $$ || exit 0
+    sleep $delay
+    kill -s SIGKILL $$
+) 2> /dev/null &
+
+exec "$@"