How to add a timeout to any Linux command

I discovered the timeout command while testing Redis connectivity in a cron job. A Redis server was unreachable, and the redis-cli command would hang indefinitely. By adding a timeout flag, I ensured the command would exit after a few seconds, avoiding unnecessary delays in the cron task.

Here’s what it looked like:

timeout 5 redis-cli -h unreachable-server ping || echo "Server is unreachable"

In this example:

• The redis-cli command is given 5 seconds to respond.
• If it doesn’t, the timeout command kills it, and the echo command logs the failure.

The timeout command is part of the GNU Coreutils package, which comes pre-installed on most Debian-based systems. If it’s missing, you can install it with:

sudo apt update
sudo apt install coreutils

The syntax is straightforward:

timeout [DURATION] [COMMAND]

• DURATION: Time limit (e.g., 5s for 5 seconds, 1m for 1 minute, 1h for 1 hour).
• COMMAND: The command you want to run.

Useful examples

1. Limit a command to 10 seconds:

timeout 10s curl http://example.com

2. Test a server’s reachability with ping:

timeout 3s ping unreachable-server

3. Chain commands with a timeout:

timeout 2m some-command && echo "Command completed" || echo "Timeout reached"

4. Force kill after timeout:

Add —signal=SIGKILL to ensure the command is terminated forcefully after the timeout:

timeout --signal=SIGKILL 5s some-long-running-command