Solved "nohup" not working when logout

[banderas20]

Hi.

I have a very simple script

#!/bin/bash
echo "Wait 120s"
sleep 120s
echo "120s elapsed" > 120.txt

I run

nohup bash wait.sh &

then the process goes to background. If I exit my SSH session and login again, there are no jobs running, and only the nohup.out file is there.

What am I missing?

Thanks!

PS: running Debian GNU/Linux 12 (bookworm)

 

[CaffeineAddict]

nohup bash wait.sh &

You don't need to execute bash to run a script, just call the script directly:

nohup wait.sh &

Secondly nohup expects a command, I don't think that applies to scripts, but in any case bash is redundant.

 

[banderas20]

Maybe it's redundant. Anyway, I don't know where to find the process once I logout and login back...

 

[CaffeineAddict]

I don't know where to find the process once I logout and login back...

Not sure but here is some info worth reading:

What's the difference between nohup and ampersand

Both nohup myprocess.out & or myprocess.out & set myprocess.out to run in the background. After I shutdown the terminal, the process is still running. What's the difference between them?

stackoverflow.com

You should be able to find it with top or htop I think to get PID and manipulate it.

 

[gvisoc]

Even though your script may not use them, bash opens IO channels with the terminal session in terms of STDIN, STDOUT and STDERR. While STDIN is not going to be a problem because nohup will automatically restrict it, STDOUT and STDERR need to be redirected to files.

Indeed, part of what could kill your script would be your "echo " sentence if you exited before it.

Try to redirect STDOUT and STDERR like this: nohup wait.sh>out.txt 2>err.txt or nohup wait.sh>combined.txt 2>&1

Both work for me.

More info on how it works here: https://www.linux.org/threads/can-i-outupt-a-sh-script-to-a-file.40364/post-160130

PS -- respect the spaces!

 

[banderas20]

Understood. I tried it and the process (not the job) still was running and ended succesfully.

Thanks for your help!

 

[Diputs]

You don't need to execute bash to run a script, just call the script directly:

nohup wait.sh &

Secondly nohup expects a command, I don't think that applies to scripts, but in any case bash is redundant.

Why would nohup behave any different if being a command or a script ?

All commands are files, no ?

 

[Diputs]

Maybe it's redundant. Anyway, I don't know where to find the process once I logout and login back...

Why would you think calling bash is necessary ?

If anywhere you see a command like:
bash somescript.sh
... there should be some context as ... what are you trying to do ? Do you want to change shell ? How did you figure it was wrong in the first place ? What if you don't have bash ? Granted that is a low chance, but 100% certain there are Unix/Linux flavors that do NOT have bash.

 

[Diputs]

Not sure but here is some info worth reading:

What's the difference between nohup and ampersand

Both nohup myprocess.out & or myprocess.out & set myprocess.out to run in the background. After I shutdown the terminal, the process is still running. What's the difference between them?

stackoverflow.com

You should be able to find it with top or htop I think to get PID and manipulate it.

What is important to understand is that nohup and & are splitting off processes ...

... but, it's not because you split off a process, that it WILL be running it the background. It CAN be running in the background, but also not any more.

Do this :

nohup sleep 1 &

and see what happens. Try to find the sleep process "running in the background". Why do you think you can't find it ?