Question

I have a linux shell script that when run from command line works perfectly but when scheduled to run via crontab, it does not give desired results.

The script is quite simple, it checks to see if mysql-proxy is running or not by checking if its pid is found using the pidof command. If found to be off, it attempts to start the proxy.

# Check if mysql proxy is off
# if found off, attempt to start it

if pidof mysql-proxy 
then
    echo "Proxy running."
else
    echo "Proxy off ... attempting to restart"
    /usr/local/mysql-proxy/bin/mysql-proxy -P 172.20.10.196:3306 --daemon --proxy-backend-addresses=172.20.10.194 --proxy-backend-addresses=172.20.10.195

    if pidof mysql-proxy
    then
        echo "Proxy started"
    else
        echo "Proxy restar failed"
    fi
fi
echo "==============================================="

The script is saved in a file check-sql-proxy.sh and has permissions set to 777. When I run the script from command line (sh check-sql-proxy.sh) it gives the desired output.

4066
Proxy running.
===============================================

The script is also scheduled to run every 5 minutes in crontab as

*/5 * * * * bash /root/auto-restart-mysql-proxy.sh > /dev/sql-proxy-restart-log.log

However, when I see the sql-proxy-restart-log.log file it contains the output:

Proxy off ... attempting to restart
Proxy restar failed
===============================================

It seems that pidof command fails to return the pid of the running application which brings the flow of script in else condition.

I am unable to figure out how to resolve this since when I run the script manually, it works fine.

Can anyone help what I am missing with regards to permissions or settings?

Thanks in advance.
Mudasser

Answer 1

Check that the shell is what you think it is (usually /bin/sh, not bash)

Also check that PATH environment variable. Usually, for cron jobs it is a good practice to fully qualify all paths to binaries, e.g.

#!/bin/bash
# Check if mysql proxy is off
# if found off, attempt to start it

if /bin/pidof mysql-proxy 

etc.