fg command in Linux

The fg command in Linux is used to bring a background job to the foreground. It allows you to interact with the process directly through the terminal.

• Resumes a background or stopped job in the foreground.
• Useful for switching back to a process that was sent to the background with bg or &.

Example:

Command:

sleep 60 &
fg %3

Output:

• sleep 60 &: starts the process in the background with job ID [3]
• fg %3: brings job 3 to the foreground and continues its execution

Syntax

fg [job_spec]

The job_spec is a way to refer to the background jobs that are currently running or suspended.

• %n: Refers to job number n.
• %str: Refers to a job that was started by a command beginning with str.
• %?str: Refers to a job that was started by a command containing str.
• %% or %+: Refers to the current job (this is the default job operated on by fg if no job_spec is provided).
• %-: Refers to the previous job.

Key Options for the fg command

1. fg [JOB_SPEC]:

This is the primary use of the fg command, bringing a specified job running in the background back to the foreground. For example, if you create a dummy job using sleep 500, you can bring it back to the foreground by referencing its job number:

Command:

jobs
sleep 500
# Press: Ctrl + Z

jobs
bg %1
jobs
fg %1

Output:

"sleep 500" is a command which is used to create a dummy job which runs for 500 seconds.

2. fg --help:

This option displays help information for the fg command, explaining usage and available options.

Command:

fg --help

Output: