logsim

logsim is a bash script which is used to guarantee that only one instance of that process can run at one time. It was intended mainly for use with shell scripting. Suppouse you have a script and you want that only one instance of that script will run at one time. This situation is typical of job launched via the cron daemon.

You can source logsim into your script or you can invoke logsim so that it can launch your script; you will be guaranteed that no other instances of your script will be run at the same time. Besides you can have logsim to redirect the standart output and the standard error of your script to different syslog channel.

Logsim was developed together with Emanuele Di Giacomo.