How to Run a Command at a Specific Time in Linux

The other day I was using rsync to transfer a large file to another system on my LAN. Since it is a very large file, it will take about 20 minutes to complete. I don't want to wait any longer, and I don't want to press CTRL+C to terminate the process. I just wanted to know if there was an easy way in Linux OS to run a command for a specific time and automatically kill it once it times out – hence this post. Please continue reading.

Run a command at a specific time in Linux

We can do this in two ways.

Method 1 – Using the timeout command

The most common method is to use the timeout command. For those who don't know, the timeout command effectively limits the absolute execution time of a process. The timeout command is part of the GNU coreutils package, so it comes preinstalled on all GNU/Linux systems.

Let's say you only want to run a command for 5 seconds and then kill it. To do this we use:

$ timeout <time-limit-interval> <command>

For example, the following command will terminate after 10 seconds.

$ timeout 10s tail -f /var/log/pacman.log

You can also omit the suffix s after the seconds. The following commands are the same as above.

$ timeout 10 tail -f /var/log/pacman.log

Other possible suffixes are:

• m stands for minutes.
• h stands for hours.
• d stands for day.
  

If you run the command tail -f /var/log/pacman.log it will continue to run until you manually end it by pressing CTRL+C. However, if you run it with the timeout command, it will automatically terminate after the given time interval. If the command is still running after the timeout, you can send a kill signal as shown below.

$ timeout -k 20 10 tail -f /var/log/pacman.log

In this case, if the tail command is still running after 10 seconds, the timeout command will send a kill signal after 20 seconds and end.

For more details, check the man page.

$ man timeout

Sometimes, a particular program may take a long time to complete and end up freezing your system. In this case, you can use this trick to automatically end the process after a certain amount of time.

Method 2 - Using the timelimit program

timelimit Executes the given command with the supplied arguments and terminates the process with the given signal after the given time. First, it sends a warning signal, and then after a timeout, it sends a kill signal.

Different from timeout, timelimit has more options. You can pass number of arguments like killsig, warnsig, killtime, warntime etc. It is available in the default repositories of Debian based systems. So, you can install it using command:

$ sudo apt-get install timelimit

For Arch based systems, it is available in AUR. So, you can install it using any AUR helper like Pacaur, Packer, Yay, Yaourt, etc.

For other distributions, please download the source here and install manually. After installing timelimit, run the following command to execute for a specific period of time, for example 10 seconds:

$ timelimit -t10 tail -f /var/log/pacman.log

If you run timelimit without any arguments, it uses the default values: warntime=3600 seconds, warnsig=15 seconds, killtime=120 seconds, killsig=9. For more details, see the man pages given at the end of this guide and the project website.

$ man timelimit

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