TIL: timeout in Bash scripts

The other day at work we had a Bash script that would set up a web server and
wait for it to be up before proceeding to the next things. The script worked
fine and we had no issues, until we had an infinite loop.

We were using the Bash built-in until to check if the web server was up:

until curl --silent --fail-with-body 10.0.0.1:8080/health; do
	sleep 1
done

This works fine. Unless our web server crashes during startup and we sleep 1
forever.

Here comes a handy utility: timeout. As the name suggests, this command adds
a timeout to other commands. You specify the time limit you want to wait for a
command and if that time passes, timeout sends a signal to terminate it and
exits with non-zero. By default, timeout sends SIGTERM, but you can change
it with the --signal flag, e.g. timeout --signal=SIGKILL 1s foo.

For example, timeout 1s sleep 5 will send the SIGTERM signal to sleep
after 1 second:

$ time timeout 1s sleep 4

real    0m1,004s
user    0m0,000s
sys     0m0,005s

$ echo $?
124

The natural thing to do then is to combine timeout and until:

timeout 1m until curl --silent --fail-with-body 10.0.0.1:8080/health; do
	sleep 1
done

The only issue is that this doesn’t work. timeout expects a killable command
and until is a shell keyword: you can’t SIGTERM until. We can’t use
timeout with any shell built-in.

The way forward is to wrap that until in a Bash process:

timeout 1m bash -c "until curl --silent --fail-with-body 10.0.0.1:8080/health; do
	sleep 1
done"

Another approach is to move the until to a separate Bash script and timeout
it:

timeout 1m ./until.sh

It’s a shame we can’t use timeout with until directly, that would be
amazing. But wrapping it in a Bash process/script gets the job done.

Keep your files stored safely and securely with the SanDisk 2TB Extreme Portable SSD. With over 69,505 ratings and an impressive 4.6 out of 5 stars, this product has been purchased over 8K+ times in the past month. At only $129.99, this Amazon’s Choice product is a must-have for secure file storage.

Help keep private content private with the included password protection featuring 256-bit AES hardware encryption. Order now for just $129.99 on Amazon!

Help Power Techcratic’s Future – Scan To Support

If Techcratic’s content and insights have helped you, consider giving back by supporting the platform with crypto. Every contribution makes a difference, whether it’s for high-quality content, server maintenance, or future updates. Techcratic is constantly evolving, and your support helps drive that progress.

As a solo operator who wears all the hats, creating content, managing the tech, and running the site, your support allows me to stay focused on delivering valuable resources. Your support keeps everything running smoothly and enables me to continue creating the content you love. I’m deeply grateful for your support, it truly means the world to me! Thank you!