Uniq

This article is about the Unix utility. For the nightclub, see UNIQ. For the insurance company, see UNIQ benefit solutions^®. For the fruit, see Ugli fruit.

uniq is a Unix utility which, when fed a text file, outputs the file with adjacent identical lines collapsed to one. It is a kind of filter program. Typically it is used after sort. It can also output only the duplicate lines (with the -d option), or add the number of occurrences of each line (with the -c option).

An example: To see the list of lines in a file, sorted by the number of times each occurs:

sort file|uniq -c|sort -n

Using uniq like this is common when building pipelines in shell scripts.

Switches

• -u Print only lines which are not repeated in the original file

• -d Print one copy only of each repeated line in the input file.

• -c Generate an output report in default style except that each line is preceded by a count of the number of times it occurred. If this option is specified, the -u and -d options are ignored if either or both are also present.