How to Use nohup in Bash: Run Commands After Logout

Use nohup before a command in bash to run it immune to hangups, allowing it to continue after logout or terminal close. The output is saved to nohup.out by default unless redirected.

Syntax

The basic syntax of nohup is:

• nohup command [arguments] &

Here:

• nohup runs the command ignoring hangup signals.
• command [arguments] is the program and its options you want to run.
• & runs the command in the background so you can continue using the terminal.

bash

nohup command [arguments] &

Example

This example runs a simple bash script that prints numbers every second. Using nohup lets it keep running after logout.

bash

nohup bash -c 'for i in {1..5}; do echo "Number $i"; sleep 1; done' &

Output

nohup: ignoring input and appending output to 'nohup.out'

Common Pitfalls

Common mistakes when using nohup include:

• Not redirecting output, which goes to nohup.out by default and may clutter your directory.
• Forgetting the & to run the command in the background, which blocks the terminal.
• Running commands that require user input, which will hang since nohup ignores input.

Correct usage example with output redirection:

bash

nohup long_running_command > output.log 2>&1 &

Output

nohup: ignoring input and appending output to 'output.log'

Quick Reference

Option	Description
nohup command &	Run command immune to hangups in background
nohup command > file 2>&1 &	Run command, redirect all output to file, in background
kill PID	Stop the running background process by its PID
jobs	List background jobs in current shell
fg %job	Bring background job to foreground

Key Takeaways

Use nohup to keep commands running after logout or terminal close.

Add & to run the command in the background and free the terminal.

Redirect output to a file to avoid cluttering nohup.out.

Avoid commands that require interactive input when using nohup.

Check running background jobs with jobs and stop them with kill.