Question

I am having a hell of a time trying to write a “kill all other daemon processes” function for use within a bash daemon. I do not ever want more than one daemon running at once. Any suggestions? This is what I have:

    #!/bin/bash

    doService(){
        while
        do  
        something
        sleep 15
        done
    }

    killOthers(){
        otherprocess=`ps ux | awk '/BashScriptName/ && !/awk/ {print $2}'| grep -Ev $$`

        WriteLogLine "Checking for running daemons."

        if [ "$otherprocess" != "" ]; then 
            WriteLogLine "There are other daemons running, killing all others."
            VAR=`echo "$otherprocess" |grep -Ev $$| sed 's/^/kill /'`
            `$VAR`
        else
            WriteLogLine "There are no daemons running."    
        fi
      }


      killOthers
      doService

It works some of the time, it doesn’t others. There is almost nothing consistent.

Answer 1

If you run your service under runit — the service mustn’t fork into the background — you’ll have a guarantee there is exactly one instance of it running. runit starts the service if it isn’t running or if it quit or crashed, stops it if you ask, keeps a pidfile around.