Bash trap not killing children, causes unexpected ctrl-c behavior - linux

Question

edit
For future readers. The root of this problem really came down to running the function in an interactive shell vs. putting it in a separate script.
Also, there are many things that could be improved in the code I originally posted. Please see comments for things that could/should have been done better.
/edit
I have a bash function intended to rerun a process in the background when files in a directory change (think like Grunt, but for general purposes). The script functions as desired while running:
The subprocess is correctly started (including any children)
On file change, the sub is killed (including children) and started again
However, on exit (ctrl-c) none of the processes are killed. Additionally, pressing ctrl-c a second time will kill the current terminal session. I'm assuming this is a problem with my trap, but have been unable to identify a reason for the issue.
Here is the code of rerun.sh
#!/bin/bash
# rerun.sh
_kill_children() {
isTop=$1
curPid=$2
# Get pids of children
children=`ps -o pid --no-headers --ppid ${curPid}`
for child in $children
do
# Call this function to get grandchildren as well
_kill_children 0 $child
done
# Parent calls this with 1, all other with 0 so only children are killed
if [[ $isTop -eq 0 ]]; then
kill -9 $curPid 2> /dev/null
fi
}
rerun() {
trap " _kill_children 1 $$; exit 0" SIGINT SIGTERM
FORMAT=$(echo -e "\033[1;33m%w%f\033[0m written")
#Command that should be repeatedly run is passed as args
args=$#
$args &
#When a file changes in the directory, rerun the process
while inotifywait -qre close_write --format "$FORMAT" .
do
#Kill current bg proc and it's children
_kill_children 1 $$
$args & #Rerun the proc
done
}
#This is sourced in my bash profile so I can run it any time
To test this, create a pair of executable files parent.sh and child.sh as follows:
#!/bin/bash
#parent.sh
./child.sh
#!/bin/bash
#child.sh
sleep 86400
Then source the rerun.sh file and run rerun ./parent.sh. In another terminal window I watch "ps -ef | grep pts/4" to see all processes for the rerun (in this example on pts/4). Touching a file in the directory triggers a restart of parent.sh and children. [ctrl-c] exits, but leaves the pids running. [ctrl-c] again kills bash and all other processes on pts/4.
Desired behavior: on [ctrl-c], kill children and exit to shell normally. Help?
--
Code sources:
Inotify idea from: https://exyr.org/2011/inotify-run/
Kill children from: http://riccomini.name/posts/linux/2012-09-25-kill-subprocesses-linux-bash/

Answer 1

This isn't a good practice to follow in the first place. Track your children explicitly:
children=( )
foo & children+=( "$!" )
...then, you can kill or wait for them explicitly, referring to "${children[#]}" for the list. If you want to get grandchildren as well, this is a good user for fuser -k and a lockfile:
lockfile_name="$(mktemp /tmp/lockfile.XXXXXX)" # change appropriately
trap 'rm -f "$lockfile_name"' 0
exec 3>"$lockfile_name" # open lockfile on FD 3
kill_children() {
# close our own handle on the lockfile
exec 3>&-
# kill everything that still has it open (our children and their children)
fuser -k "$lockfile_name" >/dev/null
# ...then open it again.
exec 3>"$lockfile_name"
}
rerun() {
trap 'kill_children; exit 0' SIGINT SIGTERM
printf -v format '%b' "\033[1;33m%w%f\033[0m written"
"$#" &
#When a file changes in the directory, rerun the process
while inotifywait -qre close_write --format "$format" .; do
kill_children
"$#" &
done
}