I have a Perl script that

• queries a database for a list of files to process
• processes the files
• and then exits

Upon startup this script creates a file (let's say script.lock), and upon exit it removes this file. I have a crontab entry that runs this script every minute. If the lockfile exists then the script exits, assuming that another instance of itself is running.

The above process works fine but I am not very happy with the robustness of this approach. Specifically, if for some reason the script exits prematurely and the lockfile is not removed then a new instance will not execute properly.

I would appreciate some advice on the following:

1. Is using the lock file a good approach or is there a better/more robust way to do this?
2. Is using crontab for this a good idea or could I better write an endless loop with sleep()?
3. Should I use the GNU 'daemon' program or the Perl Proc::Daemon module (or some other equivalent) for this?