Question

I have this user crontab (accessed via the command crontab -e):

# m h  dom mon dow   command
*/3 * * * *          sh /home/FRAPS/Desktop/cronCheck.sh

The script cronCheck.sh looks like that:

#!/bin/sh
SERVICE='Script'

if ps ax | grep -v grep | grep -i "$SERVICE" > /dev/null
then
    echo "######## $SERVICE service running, everything is fine ##################\n" >> CronReport.txt
else
    echo "$SERVICE is not running. Launching it now\n" >> CronReport.txt
    perl Script.pl 
fi

When I launch the script (cronCheck.sh) from its own directory, it works like a charm, but when cron launches it, it always “# $SERVICE service running, everything is fine ###”
despite ‘Script’ is not running.

Thanks,

Answer 1

Here’s an even better way to write that conditional:

services=$(ps -e -o comm | grep -cFi "$SERVICE")
case "$services" in
    (0) 
        # restart service
    ;;
    (1)
        # everything is fine
    ;;
    (*)
        # more than one copy is running
    ;;
esac

By using ps -e -o comm you avoid having to do the silly grep -v grep thing, because only the actual process name appears in the ps output, not the arguments. And grep -cFi counts up the matches and gives you a number, so you don’t have to deal with the exit status of a pipeline.

Also, as other posters have implied, you should lead off this script by setting the PATH variable.

PATH=/bin:/usr/bin:/sbin:/usr/sbin
export PATH

You might or might not want to put /usr/local/bin at the beginning of that list, depending on your system. Don’t do it if you don’t need anything from there.

Final piece of advice: When writing scripts that will execute without user supervision (such as cron jobs), it’s a good idea to put set -e at the beginning. That makes them exit unsuccessfully if any command fails.