How to Use fg and bg Commands in Linux for Job Control

In Linux, the fg command brings a background job to the foreground, allowing you to interact with it directly. The bg command resumes a stopped job in the background so it keeps running without blocking your terminal.

Syntax

The fg and bg commands control jobs in your shell. You can specify which job to affect by its job number.

• fg [%job_number]: Brings the specified job to the foreground. If no job number is given, it uses the most recent job.
• bg [%job_number]: Resumes the specified stopped job in the background. If no job number is given, it uses the most recent stopped job.

bash

fg [%job_number]
bg [%job_number]

Example

This example shows how to start a job, stop it, and then use bg and fg to manage it.

bash

sleep 100 &
# Starts sleep command in background
jobs
# Lists jobs with job numbers
kill -STOP %1
# Stops the job with job number 1
jobs
bg %1
# Resumes job 1 in background
jobs
fg %1
# Brings job 1 to foreground

Output

[1]+  Running                 sleep 100 &
[1]+  Stopped                 sleep 100
[1]+ sleep 100 &
sleep 100

Common Pitfalls

Common mistakes include:

• Not using % before the job number (e.g., fg 1 is wrong; use fg %1).
• Trying to use fg or bg without any jobs running or stopped.
• Confusing process IDs (PIDs) with job numbers; fg and bg use job numbers, not PIDs.

bash

fg 1
# Wrong: missing % before job number
fg %1
# Correct usage

Output

bash: fg: 1: no such job
# Then after correct usage, job resumes in foreground

Quick Reference

Command	Description	Example
fg [%job_number]	Bring a background or stopped job to the foreground	fg %1
bg [%job_number]	Resume a stopped job in the background	bg %1
jobs	List current jobs with their job numbers	jobs
kill -STOP %job_number	Stop (pause) a job	kill -STOP %1
kill -CONT %job_number	Continue a stopped job	kill -CONT %1

Key Takeaways

Use fg %job_number to bring a background job to the foreground.

Use bg %job_number to resume a stopped job in the background.

Always prefix job numbers with % when using fg or bg.

Use jobs to see current jobs and their numbers.

fg and bg work with job numbers, not process IDs.