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Diffstat (limited to 'examples/scripts/timeout3')
-rw-r--r-- | examples/scripts/timeout3 | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/examples/scripts/timeout3 b/examples/scripts/timeout3 new file mode 100644 index 0000000..5c19d2e --- /dev/null +++ b/examples/scripts/timeout3 @@ -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=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 + +# 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 "$@" |