How to kill master script from slave script?(in bash)

Question

I am trying to make a "toolkit", and what I want is for it to have an "exit" functionality. Meaning that whenever I invoke "exit", whatever I have started should stop. However, not just the toolkit script, but the main script as well. Meaning the following:

Let A.sh be the master script. At some point, A.sh will trigger B.sh, which gives the user options. I want B.sh to always have an "exit" option. When chosen, it should exit B.sh (easy, just run "exit"), but also end A.sh.

Of course, I could do something like

if [[ $(B.sh) == "exit" ]]; then exit; fi

but that is tedious at best, and generally not what a "toolkit" should do.

Any ideas how I can do it? Cheers.

Answer 1

At least on Linux, you can have the child script kill the process group of the parent. That will kill the parent itself and any child processes it may have launched. From man kill:

ARGUMENTS
       The list of processes to be signaled can be a mixture of names and
       PIDs.

[. . .]
           -n
               where n is larger than 1. All processes in process group n are
               signaled. When an argument of the form '-n' is given, and it
               is meant to denote a process group, either a signal must be
               specified first, or the argument must be preceded by a '--'
               option, otherwise it will be taken as the signal to send.

So your function can be something like this:

killGroup(){
    pgid=$(ps -p "$$" -o pgid=)
    kill -- -"$pgid"
}

That will get the process group ID, and the run kill on it to kill all processes under this group ID.

Answer 2

Clearly hackish, but to answer the question: you can reach the parent bash script by $PPID.

$ cat > A.sh
#!/bin/bash
/bin/bash B.sh
echo "A continues"
exit 0

$ cat > B.sh
#!/bin/bash
echo "B entered"
kill $PPID
sleep 3
echo "B finishes"
exit 0

$ bash A.sh
B entered
Terminated
$ B finishes

You can add a trap in A.sh to let A exit cleanly, not by SIGTERM which triggers the Terminated message from the invoking shell.

A better solution might be to set -e in A.sh which will make A.sh to terminate should any of the commands in it exit non-zero:

$ cat >A.sh
#!/bin/bash
set -e
bash B.sh
echo "A continues"
exit 0

$ cat > B.sh
#!/bin/bash
echo "B finishes with exit code 1"
exit 1

$ bash A.sh
B finishes with exit code 1

$ echo $?
1