LINUX HACK 24

Hack 24. Uniq Command

Uniq command is mostly used in combination with sort command, as uniq removes duplicates only from a sorted file. i.e In order for uniq to work, all the duplicate entries should be in the adjacent lines. Following are some common examples.

1. When you have an employee file with duplicate entries, you can do the following to remove duplicates.

$  sort  namesd.txt  |  uniq

$  sort  –u  namesd.txt

2. If you want to know how many lines are duplicates, do the following. The first field in the following examples indicates how many duplicates where found for that particular line. So, in this example the lines beginning with Alex and Emma were found twice in the namesd.txt file.

$  sort  namesd.txt  |  uniq  –c

2  Alex  Jason:200:Sales

2  Emma  Thomas:100:Marketing

1  Madison  Randy:300:Product  Development

1  Nisha  Singh:500:Sales

1  Sanjay  Gupta:400:Support

3. The following displays only the entries that are duplicates. $ sort namesd.txt | uniq –cd

2  Alex  Jason:200:Sales

2  Emma  Thomas:100:Marketing