Limiting command runtime in Linux

It is sometimes useful to limit the running time of a process, either to stop it from using up all resources or to make sure nightly cron jobs don’t continue into working hours.

I needed this for rsync, to let a remote backup server slowly catch up if large amounts of data were added to the live server during the day. A useful post on the rsync mailing list discusses an rsync patch but also the timeout command.

After installing (the Debian package is simply timeout) it is as easy as running with the number of seconds to run for:

timeout 21600 rsync -a ...

It is also possible to specify the signal which will be sent to a program, which is useful if you do not want to simply send SIGKILL. I used SIGHUP in the hope that rsync would have a chance to exit gracefully:

timeout -1 21600 rsync -a ...

A full list of signals and their numeric values can be found in man 1 kill.

A wrapper script is also available from Johannes Buchner.