I have a Cygwin bash script that I need to watch and terminate under certain conditions - specifically, after a certain file has been created. I'm having difficulty figuring out how exactly to terminate the script with the same level of completeness that Ctrl+C does, however.
Here's a simple script (called test1) that does little more than wait around to be terminated.
#!/bin/bash
test -f kill_me && rm kill_me
touch kill_me
tail -f kill_me
If this script is run in the foreground, Ctrl+C will terminate both the tail and the script itself. If the script is run in the background, a kill %1 (assuming it is job 1) will also terminate both tail and the script.
However, when I try to do the same thing from a script, I'm finding that only the bash process running the script is terminated, while tail hangs around disconnected from its parent. Here's one way I tried (test2):
#!/bin/bash
test -f kill_me && rm kill_me
(
touch kill_me
tail -f kill_me
) &
while true; do
sleep 1
test -f kill_me && {
kill %1
exit
}
done
If this is run, the bash subshell running in the background is terminated OK, but tail still hangs around.
If I use an explicitly separate script, like this, it still doesn't work (test3):
#!/bin/bash
test -f kill_me && rm kill_me
# assuming test1 above is included in the same directory
./test1 &
while true; do
sleep 1
test -f kill_me && {
kill %1
exit
}
done
tail is still hanging around after this script is run.
In my actual case, the process creating files is not particularly instrumentable, so I can't get it to terminate of its own accord; by finding out when it has created a particular file, however, I can at that point know that it's OK to terminate it. Unfortunately, I can't use a simple killall or equivalent, as there may be multiple instances running, and I only want to kill the specific instance.
/bin/kill (the program, not the bash builtin) interprets a negative PID as “kill the process group” which will get all the children too.
Changing
kill %1
to
/bin/kill -- -$$
works for me.