What signal is sent when you close a bash terminal to the programs it was running

Question

I have a Bash script that launches a Python program. The Bash script handles SIGINT, SIGTERM and SIGHUP signals to do a cleanup operation. I noticed that when I close the process in a tab in LXTerminal, the cleanup process happens. But when I close the entire terminal window, the cleanup process closes.

What am I missing to have the cleanup process to happen?

Answer 1

Here's a script that generates a script that will try to catch all signals. The script it generates (sigcatcher.sh) outputs the name of the caught signal before exiting.

#!/bin/sh

# generate a shell function for each and every available signal.

/bin/kill -l | tr ' ' '\n' |
while read signal; do
    cat <<END_OF_FUNCTION
handle_$signal () {
  echo "Caught $signal"
  exit
}

trap 'handle_$signal' $signal

END_OF_FUNCTION
done >sigcatcher.sh

echo 'echo "$$"; sleep 600' >>sigcatcher.sh

On my system (OpenBSD), /bin/kill -l generates a list of available signals on one line, that's why the tr is there to break it up.

The generated script will look something like this:

handle_HUP () {
  echo "Caught HUP"
  exit
}

trap 'handle_HUP' HUP

handle_INT () {
  echo "Caught INT"
  exit
}

trap 'handle_INT' INT

(etc.)

And it will be finished off with

echo "$$"; sleep 600

It outputs its PID and sleeps for 10 minutes.

You run it like this:

$ sh ./sigcatcher.sh >sigcatcher.out

Then you close the window, and then you inspect sigcatcher.out.

I don't run X Windows, but when I kill the tmux pane that this script is running in, I get "Caught HUP" in the output file.