Created
August 29, 2018 10:33
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Bash Script PID file locking with extra care trying to avoid simultaneous runs using a random backoff
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| #!/bin/bash - | |
| set -e | |
| scriptname=$(basename $0) | |
| pidfile="/tmp/${scriptname}.pid" | |
| if [ -d /var/run ] && [ -w /var/run ]; then | |
| pidfile="/var/run/${scriptname}.pid" | |
| fi | |
| if [ -f $pidfile ]; then | |
| pid=$(cat $pidfile) | |
| # lets try to avoid simultaneous start by random backoff | |
| random=$(od -A n -t d -N 1 /dev/random); random=$(( 1 + $random % 6 )) | |
| running=1 | |
| ps -eo pid,command | grep "^$pid.*${scriptname}" > /dev/null 2>&1 || running=0 | |
| if [ $running -eq 0 ]; then | |
| echo $$ > $pidfile | |
| sleep $random | |
| fi | |
| pid=$(cat $pidfile) | |
| if [ $$ -ne $pid ]; then | |
| running=1 | |
| ps -eo pid,command | grep "^$pid.*${scriptname}" > /dev/null 2>&1 || running=0 | |
| if [ $running -eq 1 ]; then | |
| echo "[PID $$]: ${scriptname} already running with pid ${pid}. Exiting." | |
| exit 1 | |
| fi | |
| fi | |
| fi | |
| echo $$ > $pidfile | |
| if [ $? -ne 0 ]; then | |
| echo "Could not create PID file ${pid}" | |
| exit 1 | |
| fi | |
| ### main script ### | |
| echo Main [$$] | |
| while [ 1 -eq 1 ]; do | |
| sleep 20; | |
| done |
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