Limit Linux Command Execution Time with timeout and timelimit

When a Linux command or script runs longer than desired—causing a seemingly frozen system, consuming excessive logs, or simply needing a fixed runtime—you can enforce a time limit using built‑in utilities.

Method 1: Using timeout

The GNU timeout command runs another command for a given period and then sends a signal to terminate it. It is part of the core GNU utilities and is pre‑installed on most GNU/Linux distributions.

Basic syntax: $ timeout <time‑limit> <command> Example: run tail -f /var/log/pacman.log for only 10 seconds. $ timeout 10s tail -f /var/log/pacman.log Units you can use after the number:

m – minutes

h – hours

d – days

If you omit the unit, seconds are assumed.

By default, timeout sends SIGKILL when the limit expires, but you can choose a different signal with the -k option. $ timeout -k 20 10 tail -f /var/log/pacman.log In this example, after 10 seconds a SIGTSTP (signal 20) is sent.

To see all signal names, run: $ kill -l The command is also handy for hardware debugging, e.g., to capture kernel messages for 10 seconds: $ timeout 10 dmesg -w For more options, consult the manual page:

$ man timeout

Method 2: Using timelimit

The timelimit utility offers similar functionality with additional flexibility, such as specifying the signal to send and the number of times to send it.

It is not installed by default on many distributions. On Debian‑based systems, install it with: $ sudo apt-get install timelimit After installation, the equivalent command becomes: $ timelimit -t10 tail -f /var/log/pacman.log If invoked without parameters, timelimit uses these defaults:

warntime = 3600 seconds

warnsig = 15

killtime = 120 seconds

killsig = 9

For detailed usage, read its manual page:

$ man timelimit