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

In bash, fg brings a background job to the foreground, letting you interact with it directly, while bg resumes a stopped job in the background so it keeps running without blocking your terminal. These commands help manage multiple tasks in one shell session.

Syntax

The fg and bg commands control jobs in bash. 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, then resume it in the background and bring it back to the foreground.

bash

sleep 100 &
# Starts sleep in the background
jobs
# Lists jobs
kill -STOP %1
# Stops the job 1
jobs
# Shows stopped job
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]+  Running                 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 on jobs that do not exist or are already running in the foreground.
• Confusing process IDs with job numbers; fg and bg use job numbers shown by jobs.

bash

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

Output

bash: fg: 1: no such job
# then after correct command, job resumes in foreground

Quick Reference

Command	Description	Example
fg [%job]	Bring job to foreground	fg %2
bg [%job]	Resume stopped job in background	bg %1
jobs	List current jobs with numbers	jobs
kill -STOP %job	Stop a job	kill -STOP %1
kill -CONT %job	Continue a stopped job	kill -CONT %1

Key Takeaways

Use fg %job_number to bring a background or stopped 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 before using fg or bg.

Stopping a job with kill -STOP %job lets you control when to resume it.