CODEWITHSUNDEEP
bashbackground-processnohup
applecider
applecider

Reputation: 2471

How to prevent nohup from "clogging" the command line?

I want to write a bash script that runs two commands in the background. I am using nohup for this:

nohup cmd1 &
nohup cmd2 &

However, only the 1st command runs in the background.

When I run nohup cmd1 & manually in the command line. First, I type nohup cmd1 & then hit enter; this starts the process:

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But, then I need to hit enter again to be able to type another command:

enter image description here

I think this is "clogging" up the command line, and is causing my bash script to get stuck at the first nohup ... & command.

Is there a way to prevent this?

Upvotes: 3

Views: 2580

Answers (2)

hek2mgl
hek2mgl

Reputation: 158250

Let me say something to nohup because I'm not sure if you are certain about what it is doing. In short, the nohup command is not necessary to run a process in background. The ampersand at the end of the line is doing it.

nohup prevents the background process from receiving SIGHUP (hup for hang up) if you close the terminal where the starting shell runs it. SIGHUP would effectively terminate the process.

If started with nohup the process will not receive that event and will continue running, owned by the init process (pid 1) if the terminal will being closed.

Furthermore the nohup command will redirect standard output of the controlled process to a file, meaning it will not appear on screen any more. By default this file is called nohup.out.

Upvotes: 2

Keith Thompson
Keith Thompson

Reputation: 263637

Nothing is "clogged". The first command, running in the background, prints some output after your shell prints its next prompt. The shell is waiting for you to type a command, even though the cursor is no longer on the same line as the prompt. That extra Enter is an empty command, causing the shell to print another prompt. It's harmless but unnecessary.

Upvotes: 4

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