Uniq

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This article is about the Unix utility. For the nightclub, see UNIQ. 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.

• -i Ignore case differences when comparing lines

• -s Skips a number of characters in a line

• -w Specifies the number of characters to compare in lines, after any characters and fields have been skipped

• --help Displays a help message

• --version Displays version number on stdout and exits.

See also

• List of Unix programs

External links

• uniq's manpageit:Uniq