bg Command: Tutorial & Examples
The bg
command stands for "background" and is used to
resume paused or stopped jobs and run them in the background. It's a part of job control commands in
a shell along with fg
, jobs
, and Ctrl+z
key
combination.
Understanding How bg
Works
When you run a command or a process in the shell, that process is typically run in the foreground.
This means you can't use the shell for other commands or tasks until this process is completed. With the bg
command,
you can send this process to the background and free up your shell for other tasks.
For instance, if a process is paused or stopped using the Ctrl+z
key combination, you can use the bg
command to
resume the process in the background. This process now runs independently of the shell, allowing you to continue using
the shell for other tasks.
Why bg
Command is Important
The bg
command is crucial in multitasking in a Linux environment. It allows users to run time-consuming tasks without
blocking the shell, thus optimizing the usage of system resources. This ability is especially useful when managing Linux
servers, as it allows administrators to run multiple scripts or tasks concurrently.
How to Use bg
Command
Using the bg
command is straightforward. When a process is paused or stopped, you can use the bg
command followed by
the job number to resume it in the background. Here's an example:
$ sleep 100
^Z
[1]+ Stopped sleep 100
$ bg %1
In this example, the sleep 100
command is paused using the Ctrl+z
key combination. The job number is 1
.
The bg %1
command then resumes the job in the background.
Common bg
Command Parameters
The bg
command doesn't have many parameters. The most common usage is bg %jobnumber
. Here, %jobnumber
is the job
number that you want to resume in the background. You can get the job number from the output when you stop a job or by
using the jobs
command.
Potential Problems and Pitfalls with bg
Command
While bg
command is generally safe to use, be aware that moving a process to the background could cause unexpected
behavior if the process requires user interaction. Also, background processes are paused if they try to read input from
the user.
Moreover, it's important to remember that if you close the parent shell, all background jobs will be terminated. To
avoid this, use the nohup
command or tools like screen
or tmux
.
Wrapping Up
In conclusion, bg
command is a powerful tool for managing processes in a Linux environment. It allows you to multitask
and make the most of your system resources. As with any command, it's important to understand how it works and when to
use it. With practice, you'll find the bg
command becoming a regular part of your Linux command toolkit.