I would like to try trapping signal 1 but fail
#!/bin/bash
# capture an interrupt # 0
trap 'echo "Exit 0 signal detected..."' 0
trap 'echo "Exit 1 signal detected..."' SIGHUP
# display something
echo "This is a checkpoint 1"
exit 1
echo "This is checkpoint 2"
# exit shell script with 0 signal
exit 0
Output--
kithokit@15:02:55 trunk (master) $ ./test.sh
This is a checkpoint 1
Exit 0 signal detected...
kithokit@15:03:44 trunk (master) $
Even if it is exit 1, it always trap into trap 0, any one knows how to solve this?
Thanks
exit 1 does not send a SIGHUP. It exits with return code (AKA exit status) 1. To send a SIGHUP use kill:
#!/bin/bash
# capture an interrupt # 0
trap 'echo "Signal 0 detected..."' 0
trap 'echo "SIGHUP detected..."' SIGHUP
# display something
echo "This is a checkpoint 1"
kill -1 $$
echo "This is checkpoint 2"
# exit shell script with 0 signal
exit 0
$$ is the ID of the current process. So, kill -1 $$ sends signal 1 (SIGHUP) to the current process. The output of the above script is:
This is a checkpoint 1
SIGHUP detected...
This is checkpoint 2
Signal 0 detected...
If the goal is to check the return code (also known as exit status) rather than to catch special signals, then all we need to do is check the status variable $? on exit:
#!/bin/bash
# capture an interrupt # 0
trap 'echo "EXIT detected with exit status $?"' EXIT
echo "This is checkpoint 1"
# exit shell script with 0 signal
exit "$1"
echo "This is checkpoint 2"
When run at the command line, this produces:
$ status_catcher 5
This is checkpoint 1
EXIT detected with exit status 5
$ status_catcher 208
This is checkpoint 1
EXIT detected with exit status 208
Note that the trap statement can call a bash function which could include arbitrarily complicated statements to process different return codes differently.