This is part of the Semicolon&Sons Code Diary - consisting of lessons learned on the job. You're in the unix category.
Last Updated: 2024-11-21
You can stop a single process with kill. E.g.
kill pid # e.g. kill 808
# or kill -9 pid e.g. kill -9 808
# or kill -SIGTERM pid
But say you wanted to kill a whole process group. Then use a negative number of
the process group id (and -- to offset the negative number)
kill -- -$PGID # e.g. kill -- -19701
Why might you want to do this? Basically because killing a parent process in
unix does not kill children. Rather the children become orphaned and re-parented
by init. In order to kill child processes, you need to kill the process group
they belong to.
There is one confusing thing to be aware of: sending SIGINT (e.g. Control-C, AKA
the interrupt character ^c) sends a signal to whole process group in the
foreground. And, BTW, whenever you run a program in the foreground (e.g. cat
or top), the shell is basically out of the way and waiting; it does nothing to
facilitate your interaction with these programs (that this happens is aa common
misconception). That's why your SIGINT signal does not affect your shell too.
However, the shell knows to become active again because it receives SIGCHLD in
its role as parent process. Note that the shell IS a parent process, but is
NOT a part of the same process group. It is however, a session leader (same
SID)