Say I have two scripts that just print back the return code from a useless subscript:
script1
(echo; exit 0)
echo $?
script2
(echo)
echo $?
Both give back 0. But is there a way to tell that the first subscript explicitly uses the exit command?
After some research I got some breakthrough. Namely you can setup an exit_handler that can tell if there was an exit call by simply examining the last command.
#! /bin/bash
exit_handler () {
ret=$?
if echo "$BASH_COMMAND" | grep -e "^exit " >> /dev/null
then
echo "it was an explicit exit"
else
echo "it was an implicit exit"
fi
exit $ret
}
trap "exit_handler" EXIT
exit 22
This will print
it was an explicit exit
Now in order to tell the parent, instead of echoing, we can rather write to a file, a named pipe or whatever.
As per noting of choroba, exit without an argument will give implicit call, which is admittedly wrong since exit (without argument) is the same as exit $?. For that reason the regex has to take that into consideration:
#! /bin/bash
exit_handler () {
ret=$?
if echo "$BASH_COMMAND" | grep -e "^exit \|^exit$" >> /dev/null
then
echo "it was an explicit exit"
else
echo "it was an implicit exit"
fi
exit $ret
}
trap "exit_handler" EXIT
exit 22
exit_handler() in each script1 and script2. What if the last command in script2 is echo "It is now time to exit"?
^exit since the regex allows only a command that starts with exit followed by a space. The only command that could be is exitShell Variables section of man bash. I think you hit upon a good solution. The only curiosity I have is the way it is described in BASH_COMMAND, specifically, it is the command executing at the time of the trap. Obviously it is working, but it would be reassuring to see it is the last command executed before the time of the trap. Oh well, I still like it :)
22, I get 'implicit exit'.
exityourself).trap "rm -f $tmpfile; exit" 0?! This is an common practice remove temp-files at exit, and your "exit_trap" will be overwritten. Simply, this isn't a good idea - bad logic and wrong solution and as someone already told you X-Y problem...