The "uniq" Utility
July 19, 1998
Like the comm utility, the "uniq" utility is used
to find repetition. However, the "uniq" utility is used to find
repeated lines within a file rather than between two files. The "uniq"
utility is used to find adjacent duplicate lines and (usually) remove
them. The usual syntax looks something like:
uniq options filename optional_new_filename
If no optional_new_filename is specified, the output of
uniq will be printed to standard output.
As you might expect, it is most common to run
the uniq utility after having already sorted the file. Below is
an example on how you might use the "uniq" utility.
![[uniq Example]](Images/uniq.gif)
The "uniq" utility comes with several useful
utilities. The more common ones are described below.
| Option |
Explanation |
| -c |
Produces a columnar output in which the left column reports the
number of times the line was repeated |
| -d |
Displays one copy of each repeated line, but does not display
non-repeated lines. |
| -u |
Non repeated lines are displayed, but repeated lines are not.
|
Consider the following examples:
![[uniq Options Example]](Images/uniq_options.gif)
The "comm" Utility
Introduction to UNIX for Web Developers | Table of Contents
The "spell" Utility
|
