How to send a process to the background

Sending a process to the background in Linux is quite easy. All you need is bg, fg, &, and ctrl+Z ( ^Z ).

For this example I will use a simple bash script test.sh I put together to print “Test” every 5 seconds.

#!/bin/bash
#This script will print "Test" every 5 seconds
#
while [ true ]
do
echo “Test at `date`”
sleep 5
done
#End

Now let’s see how it’s done.

[user@abubu root]$./test.sh &
This starts test.sh and sends it to the background. You will be back at shell but should see the “Test” message every 5 seconds.

[user@abubu root]$jobs
[1]+ Running ./test.sh &
The jobs command will print all the background processes. Each process is represented by a number to it’s left. For example, tesh.sh is represented by 1.

[user@abubu root]$fg 1
The fg command will send the test.sh process to the foreground and return control to the shell.

[user@abubu root]$ ./test.sh (hit ctrl+Z (^Z) now)
Test at Tue Jun 3 15:11:38 MYT 2008
[1]+ Stopped ./test.sh
The test.sh process is temporarily suspended.

[user@abubu root]$bg 1
The bg command will send test.sh to the background.

[user@abubu root]jobs
[1]+ Running ./test.sh &
The jobs command will print all the background processes. Each process will be represented by a number to it’s left. tesh.sh is represented by 1.

[user@abubu root]$fg 1
The fg command will send the test.sh process to the foreground and return control to the shell.

That’s it.