Send "sigterm" from Java to Bash script

Question

I am starting a Java code from Bash script called start.sh. The Bash script fires up the Java code and then the Java code runs. At the end of the Java program, I want to send a signal back to the Bash script to terminate. Keep in mind that the Bash script runs with PID = 1. And I have to kill the PID 1 process.

I have the bash script set up such that it runs in an infinite loop and waits for a termination signal:

#!/bin/bash

# Run the java code here..

# Listen for an exit command.

trap 'exit 0' SIGTERM
while true; do :; done

I am using Docker instances and the signal is sigterm. I am following this tutorial: https://www.ctl.io/developers/blog/post/gracefully-stopping-docker-containers/ which explains how to send a sigterm from command line. I want to automate this process and close/kill the docker instance from inside as soon as the Java program ends.

How do I send the signal back to the bash script that started the Java code in the first place?

Should I follow this method to send a signal as arguments to the bash script? Or will it start another bash script with a different PID (not 1).

Help needed!

No sorry, read it the wrong way round, as in send it to java from bash. — 123
– 123, Commented Apr 20, 2016 at 10:23
The thing is, I can terminate (send sigterm) easily from outside to the docker instance. lt terminates as required. I just wanna send it from Java and automate it so I don't have to write any sigterm command and keep checking if the java program has finished or not — Mohammad Sohaib
– Mohammad Sohaib, Commented Apr 20, 2016 at 10:26

evtuhovdo · Accepted Answer · 2016-04-22 10:43:30Z

0

Write 'set -e' in second line in bash script.
Dont use trap and while. Replace it by 'exec your_java_code_run'.

By this way docker get SIGTERM after java code run end.

Exemple:

#!/usr/bin/env bash
set -e

someOtherCodeIfNeed

exec your_java_code_run

edited Apr 22, 2016 at 10:43

answered Apr 21, 2016 at 18:56

evtuhovdo

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3 Comments

Mohammad Sohaib Over a year ago

something like this: #!/bin/bash set -e # Run the java code here.. exec HelloWorld ?

evtuhovdo Over a year ago

#!/usr/bin/env bash set -e someOtherCode exec HelloWorld

evtuhovdo Over a year ago

When your_java_code_run finish conteiner will die =)

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