What is the easiest way to "detach/daemonize" a Bash script?

bash process daemon sleep detach
Warpling picture Warpling · Dec 6, 2010 · Viewed 22.9k times · Source

What I am trying to do is write a Bash script that sleeps for a set amount of time before using the mac say command to speak some text.

I'd like to be able to run the command and then close the terminal so it will still speak at the set time. I've looked into nohup, detach, launchd, and putting the process in the background, but all of these solutions still result in the process being terminated once the terminal is closed. Should I somehow make some sort of zombie child process to do this? What is the best solution? Thank you

# Simple Example of main code
sleep 10;
say hello;
exit;

Answer

Jonathan Leffler picture Jonathan Leffler · Dec 6, 2010

Section 3.7.6 of the Bash Manual says:

The shell exits by default upon receipt of a SIGHUP. Before exiting, an interactive shell resends the SIGHUP to all jobs, running or stopped. Stopped jobs are sent SIGCONT to ensure that they receive the SIGHUP. To prevent the shell from sending the SIGHUP signal to a particular job, it should be removed from the jobs table with the disown builtin (see Section 7.2 [Job Control Builtins], page 88) or marked to not receive SIGHUP using disown -h.

So, using either nohup or disown should do the trick. Or you can do:

trap "" 1
sleep 10
say hello

That 'trap' line ignores signal 1, SIGHUP; you can probably also write 'trap "" HUP".

Related questions

How to wait in bash for several subprocesses to finish and return exit code !=0 when any subprocess ends with code !=0?

How to wait in a bash script for several subprocesses spawned from that script to finish and return exit code !=0 when any of the subprocesses ends with code !=0 ? Simple script: #!/bin/bash for i in `seq 0 9`; do doCalculations $i & …

Read More
How to check if a process id (PID) exists

In a bash script, I want to do the following (in pseudo-code): if [ a process exists with $PID ]; then kill $PID fi What's the appropriate expression for the conditional statement?

Read More
Linux/Unix command to determine if process is running?

I need a platform independent (Linux/Unix|OSX) shell/bash command that will determine if a specific process is running. e.g. mysqld, httpd... What is the simplest way/command to do this?

Read More