Hacker News Reader

Comment by thomasbacklund | Hacker News Reader

Indeed, it's such a messy job coding for shell..

Comes with a lot trial and error.

The above will work as (tested in ash/dash/bash):

  #!/usr/bin/env sh
  trap "echo exiting" INT
  sleep 1h

But to your point, yes, how to actually know that without doing trial n' error & stackoverflow.

Thanks for the `sleep 1h`, didn't know that you could do hour as unit :)

(edited: turned out INT is enough to trap)

View on HN

Nope, INT is (generally) too specific :)

Sometimes of course, you just want to run something on SIGINT and not on normal exit, SIGHUP or whatever. But maybe the main use case for trap is implementing try/finally logic and you really want it to fire whenever the shell exits, not matter how (to clean up resources like temporary files). Bash's `trap EXIT` mostly does what you want ("run this when the shell exits"), but writing something that behaves this way across shells (and doesn't fire multiple times etc). is amazingly painful.

Ok, I though it was to catch CTRL-c :)

trap EXIT, does work for me in ash/dash/bash, though, when just letting the code flow exit with and without errors.

Not sure your use case, but I can for sure concur that traps are very painful to get right, especially when getting into child/grandchild processes land, taking terminal session, etc in regard.

Reply on news.ycombinator.com