Forward TERM signal to all sub-processes

README.md

Forward TERM signal to all sub-processes

It only requires you to prepend all commands with run, then if the script process is TERM, it will forward the signal to the processes you instanciated using the run command if they are still alive, if they are not, they are just ignored.

This was designed to make docker containers shutdown faster when you have a starting script to run (in this example we are running npm install and npm start), this works because when requested to stop the container, docker will send a TERM signal to the process with id 1, which is the first command ran by the CMD (CMD ["this_command_here.sh"]).

So if this script receives TERM it will forward it leading every process to shutdown, so the container can die peacefully.

References:

• https://www.ctl.io/developers/blog/post/gracefully-stopping-docker-containers/
• https://dirask.com/posts/Bash-forward-SIGTERM-to-child-processes-DkBqq1

startup.sh

#!/bin/sh
set -e

PIDS_FILE="/tmp/pids"
run() {
    echo "$*"                # feedback of execution
    "$@" &                   # async execution
    pid=$!                   # save pid
    echo "$pid" >>$PIDS_FILE # store pid
    wait "$pid"              # await pid
}

terminate() {
    # forward TERM signal to all subprocesses whose pid reside on $PIDS_FILE
    xargs -f $PIDS_FILE -I{} "kill -TERM '{}' 2> /dev/null"
}
trap terminate TERM

run npm install
run npm start