fg and bg commands in Linux CLI - Step-by-Step Execution

Concept Flow - fg and bg commands

Start a command in shell

↓

Press Ctrl+Z to suspend

↓

Job is stopped and moved to background

↓

Use 'bg' to resume job in background

↓

Job runs in background

↓

Use 'fg' to bring job to foreground

↓

Job runs in foreground

↓

Job completes or suspended again

This flow shows how a running command can be suspended, then resumed in background with 'bg' or brought back to foreground with 'fg'.

Execution Sample

Linux CLI

sleep 100
# Press Ctrl+Z
bg
fg

Starts a sleep command, suspends it, resumes in background, then brings it back to foreground.

Execution Table

Step	Action	Shell Output	Job State	Foreground/Background
1	Run 'sleep 100'	No output	Running	Foreground
2	Press Ctrl+Z	[1]+ Stopped sleep 100	Stopped	Suspended
3	Run 'bg'	[1]+ sleep 100 &	Running	Background
4	Run 'fg'	sleep 100	Running	Foreground
5	Job completes or user interrupts	No output	Done	Foreground

💡 Job finishes or is interrupted, shell prompt returns.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
Job State	Running	Stopped	Running	Running	Done
Foreground/Background	Foreground	Suspended	Background	Foreground	Foreground

Key Moments - 3 Insights

Why does the job stop after pressing Ctrl+Z?

Pressing Ctrl+Z sends a stop signal to the job, suspending it (see Step 2 in execution_table). The shell marks it as stopped and frees the terminal.

What is the difference between 'bg' and 'fg'?

'bg' resumes the stopped job in the background allowing you to keep using the shell (Step 3). 'fg' brings the job back to the foreground so it can interact with the terminal (Step 4).

Can you run multiple jobs in background?

Yes, each job can be suspended and resumed independently with 'bg' or 'fg'. The shell tracks jobs by numbers (not shown here).

Visual Quiz - 3 Questions

Look at the execution_table, what is the job state after pressing Ctrl+Z?

A Stopped

B Running

C Done

D Background

💡 Hint

Check Step 2 in execution_table under 'Job State'

At which step does the job run in the background?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at 'Foreground/Background' column in execution_table

If you skip 'bg' and run 'fg' immediately after Ctrl+Z, what happens?

A Job resumes in background

B Job stays stopped

C Job resumes in foreground

D Shell shows error

💡 Hint

Recall 'fg' brings job to foreground regardless of background state (see Step 4)

Concept Snapshot

fg and bg commands manage job control in the shell.
Ctrl+Z suspends a running job (stops it).
'bg' resumes the job in background (no terminal control).
'fg' resumes the job in foreground (terminal control).
Use these to multitask in the shell.

Full Transcript

This lesson shows how to control jobs in a Linux shell using fg and bg commands. When you run a command like 'sleep 100', it runs in the foreground. Pressing Ctrl+Z suspends the job, stopping it and freeing the terminal. The shell marks the job as stopped. You can then use 'bg' to resume the job in the background, letting you keep using the shell prompt. Alternatively, 'fg' brings the job back to the foreground so it can interact with the terminal again. The execution table traces these steps, showing job states and whether the job runs in foreground or background. Key moments clarify why Ctrl+Z stops the job, the difference between fg and bg, and that multiple jobs can be managed this way. The visual quiz tests understanding of job states and command effects. The quick snapshot summarizes the commands and their use for job control.