Linux bg Command: Resume a Shell Job in the Background
bg resumes a stopped job in the background in Bash. It is used when you want to stop a running command with Ctrl+Z and continue using the terminal.
What is the bg command?
bg sends a continue signal to a stopped job but does not give front control of the terminal. You can check the job number with jobs and specify it like %1. Interactive programs waiting for input may stop again in the background.
Basic syntax
bg [%job number]
The installed implementation and options may vary depending on the distribution. Check the description for your system with help bg.
Examples
Checking stopped jobs
After pressing Ctrl+Z during a foreground command execution, check the status.
jobs -s
Resuming a specific job in the background
In the example, replace %1 with the actual number from the jobs output.
bg %1
Check resume result
Check if it is in the Running state.
jobs -l
Running a Paused Job in the Background
bg continues a job that is currently paused in the background of the current shell. For example, after running sleep 60 and stopping it with Ctrl+Z, check the job number.
jobs bg %1 jobs
Example of state changes:
[1]+ Stopped sleep 60 [1]+ Running sleep 60 &
%1 refers to job number 1 in the current shell, not the PID. If the shell does not support job control or there are no paused jobs, bg will fail. When a job finishes, it may disappear from jobs, so check the status again.
Main Options and Format
| Options/Format | Description |
|---|---|
%N |
Specify job number N of the current shell. |
%+ |
Specify the current job. |
%- |
Specify the previous job. |
Omit argument |
Use the job that Bash considers the current job. |
Precautions when using
A job stopped with Ctrl+Z is not yet running. A job that tries to read from standard input may be stopped again even if resumed with bg. bg is a shell job control feature and cannot be applied to processes started in another terminal.
Frequently Asked Questions
Are appending & at the end of a command and using bg the same?
& starts the command in the background from the beginning, while bg resumes a currently stopped job in the shell in the background.
Official Documentation
The exact behavior of these options and implementation differences can be found in the official bg documentation.
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