Created
April 19, 2014 07:22
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A template to write a quick daemon as a bash script
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#!/bin/sh | |
# This is a skeleton of a bash daemon. To use for yourself, just set the | |
# daemonName variable and then enter in the commands to run in the doCommands | |
# function. Modify the variables just below to fit your preference. | |
daemonName="DAEMON-NAME" | |
pidDir="." | |
pidFile="$pidDir/$daemonName.pid" | |
pidFile="$daemonName.pid" | |
logDir="." | |
# To use a dated log file. | |
# logFile="$logDir/$daemonName-"`date +"%Y-%m-%d"`".log" | |
# To use a regular log file. | |
logFile="$logDir/$daemonName.log" | |
# Log maxsize in KB | |
logMaxSize=1024 # 1mb | |
runInterval=60 # In seconds | |
doCommands() { | |
# This is where you put all the commands for the daemon. | |
echo "Running commands." | |
} | |
################################################################################ | |
# Below is the skeleton functionality of the daemon. | |
################################################################################ | |
myPid=`echo $$` | |
setupDaemon() { | |
# Make sure that the directories work. | |
if [ ! -d "$pidDir" ]; then | |
mkdir "$pidDir" | |
fi | |
if [ ! -d "$logDir" ]; then | |
mkdir "$logDir" | |
fi | |
if [ ! -f "$logFile" ]; then | |
touch "$logFile" | |
else | |
# Check to see if we need to rotate the logs. | |
size=$((`ls -l "$logFile" | cut -d " " -f 8`/1024)) | |
if [[ $size -gt $logMaxSize ]]; then | |
mv $logFile "$logFile.old" | |
touch "$logFile" | |
fi | |
fi | |
} | |
startDaemon() { | |
# Start the daemon. | |
setupDaemon # Make sure the directories are there. | |
if [[ `checkDaemon` = 1 ]]; then | |
echo " * \033[31;5;148mError\033[39m: $daemonName is already running." | |
exit 1 | |
fi | |
echo " * Starting $daemonName with PID: $myPid." | |
echo "$myPid" > "$pidFile" | |
log '*** '`date +"%Y-%m-%d"`": Starting up $daemonName." | |
# Start the loop. | |
loop | |
} | |
stopDaemon() { | |
# Stop the daemon. | |
if [[ `checkDaemon` -eq 0 ]]; then | |
echo " * \033[31;5;148mError\033[39m: $daemonName is not running." | |
exit 1 | |
fi | |
echo " * Stopping $daemonName" | |
log '*** '`date +"%Y-%m-%d"`": $daemonName stopped." | |
if [[ ! -z `cat $pidFile` ]]; then | |
kill -9 `cat "$pidFile"` &> /dev/null | |
fi | |
} | |
statusDaemon() { | |
# Query and return whether the daemon is running. | |
if [[ `checkDaemon` -eq 1 ]]; then | |
echo " * $daemonName is running." | |
else | |
echo " * $daemonName isn't running." | |
fi | |
exit 0 | |
} | |
restartDaemon() { | |
# Restart the daemon. | |
if [[ `checkDaemon` = 0 ]]; then | |
# Can't restart it if it isn't running. | |
echo "$daemonName isn't running." | |
exit 1 | |
fi | |
stopDaemon | |
startDaemon | |
} | |
checkDaemon() { | |
# Check to see if the daemon is running. | |
# This is a different function than statusDaemon | |
# so that we can use it other functions. | |
if [ -z "$oldPid" ]; then | |
return 0 | |
elif [[ `ps aux | grep "$oldPid" | grep -v grep` > /dev/null ]]; then | |
if [ -f "$pidFile" ]; then | |
if [[ `cat "$pidFile"` = "$oldPid" ]]; then | |
# Daemon is running. | |
# echo 1 | |
return 1 | |
else | |
# Daemon isn't running. | |
return 0 | |
fi | |
fi | |
elif [[ `ps aux | grep "$daemonName" | grep -v grep | grep -v "$myPid" | grep -v "0:00.00"` > /dev/null ]]; then | |
# Daemon is running but without the correct PID. Restart it. | |
log '*** '`date +"%Y-%m-%d"`": $daemonName running with invalid PID; restarting." | |
restartDaemon | |
return 1 | |
else | |
# Daemon not running. | |
return 0 | |
fi | |
return 1 | |
} | |
loop() { | |
# This is the loop. | |
now=`date +%s` | |
if [ -z $last ]; then | |
last=`date +%s` | |
fi | |
# Do everything you need the daemon to do. | |
doCommands | |
# Check to see how long we actually need to sleep for. If we want this to run | |
# once a minute and it's taken more than a minute, then we should just run it | |
# anyway. | |
last=`date +%s` | |
# Set the sleep interval | |
if [[ ! $((now-last+runInterval+1)) -lt $((runInterval)) ]]; then | |
sleep $((now-last+runInterval)) | |
fi | |
# Startover | |
loop | |
} | |
log() { | |
# Generic log function. | |
echo "$1" >> "$logFile" | |
} | |
################################################################################ | |
# Parse the command. | |
################################################################################ | |
if [ -f "$pidFile" ]; then | |
oldPid=`cat "$pidFile"` | |
fi | |
checkDaemon | |
case "$1" in | |
start) | |
startDaemon | |
;; | |
stop) | |
stopDaemon | |
;; | |
status) | |
statusDaemon | |
;; | |
restart) | |
restartDaemon | |
;; | |
*) | |
echo "\033[31;5;148mError\033[39m: usage $0 { start | stop | restart | status }" | |
exit 1 | |
esac | |
exit 0 |
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For anyone wanting to get around the broken
echo
formatting, you can add an-e
flag to theecho
command to get it to print the formatted output:echo -e "\033[31;5;148mError\033[0m: usage $0 { start | stop | restart | status }"