nohup for persistent processes in Linux CLI - Step-by-Step Execution

Concept Flow - nohup for persistent processes

Start command with nohup

↓

Ignore hangup signal

↓

Redirect output to nohup.out

↓

Run command in background (&)

↓

Process keeps running after logout

↓

Check nohup.out for output

The flow shows how nohup runs a command ignoring hangup signals, redirects output, runs in background, and keeps running after logout.

Execution Sample

Linux CLI

nohup sleep 10 &
ps
cat nohup.out

Runs sleep 10 ignoring hangup, lists processes, then shows output file content.

Execution Table

Step	Action	Command/Signal	Result	Output
1	Start command with nohup	nohup sleep 10 &	sleep runs ignoring hangup	nohup: ignoring input and appending output to 'nohup.out'
2	List processes	ps	Shows sleep process running	PID TTY TIME CMD ... sleep 10
3	Check nohup output file	cat nohup.out	File is empty (sleep has no output)
4	Logout user	exit	sleep continues running
5	After 10 seconds	ps	sleep process gone (finished)

💡 sleep 10 finishes after 10 seconds, process ends

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 4	Final
sleep_process	not running	running (ignores hangup)	running	running after logout	stopped after 10s

Key Moments - 3 Insights

Why does the process keep running after logout?

Because nohup ignores the hangup signal sent on logout, as shown in execution_table step 4.

Where does the output of the command go?

Output is redirected to nohup.out file by default, as shown in execution_table step 1.

What happens if the command produces no output?

nohup.out remains empty, as shown in execution_table step 3 with sleep command.

Visual Quiz - 3 Questions

Look at the execution table, what message does nohup print when starting the command?

A Command not found

B Process started successfully

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

D Output redirected to /dev/null

💡 Hint

Check execution_table row 1, Output column.

At which step does the process continue running after the user logs out?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Look at execution_table step 4, Result column.

If the command produced output, where would you find it?

A In nohup.out file

B In the terminal only

C In /var/log/syslog

D Nowhere, output is discarded

💡 Hint

See execution_table step 1, Output column about output redirection.

Concept Snapshot

nohup runs a command ignoring hangup signals
Redirects output to nohup.out by default
Use & to run command in background
Process keeps running after logout
Check nohup.out for command output

Full Transcript

The nohup command lets you run a process that keeps running even after you log out. It ignores the hangup signal sent when you exit the shell. When you run 'nohup sleep 10 &', it starts the sleep command in the background and redirects any output to a file called nohup.out. You can check running processes with 'ps' and see the output file with 'cat nohup.out'. Even if you log out, the sleep command keeps running until it finishes after 10 seconds.