For a client I needed to run a specific script every 10seconds. 24/24 and 7/7. A task I would normally perform with crons. But sadly enough, a cron can only be started once per minute. So I wrote a ‘runner’ script. A script that starts the other script

Things this script does:

• runs the child script 10s after the end of the previous try
• sends an e-mail if stderr is returned
• if the runner would stop, it will auto restart (due to a cronjob)
• only one instance will run at the same time.

#!/bin/bash
sleep=10
if ! ps -p $(cat /path/to/runner.pid);
  then
    echo $$ > /path/to/runner.pid
    while :
     do
        error=$(/path/to/script 2>&1 >/dev/null)
        if [ -n "$error" ];
          then
            echo "$error" | mail -s "<subject>" <to@mymailaddres.tld> -- -f <from@thisaddress.tld>
        fi
        sleep $sleep
    done
fi

Of course you can choose the time to restart the script by editing the ‘sleep’ value.
In the cronfile I added the following line:

*/30  * * * *  /path/to/runner 2>&1 >/dev/null

This way the runner script can only be ‘offline’ for 30min! Which is still acceptable.