Join command combines lines from two files based on a common field.
In the example below, we have two files – employee.txt and salary.txt. Both have employee-id as common field. So, we can use join command to combine the data from these two files using employee-id as shown below.
$ cat employee.txt 100 Jason Smith 200 John Doe 300 Sanjay Gupta 400 Ashok Sharma $ cat bonus.txt 100 $5,000 200 $500 300 $3,000 400 $1,250 $ join employee.txt bonus.txt 100 Jason Smith $5,000 200 John Doe $500 300 Sanjay Gupta $3,000 400 Ashok Sharma $1,250