uniq(1)

NAME

uniq — report repeated lines in a file

SYNOPSIS

uniq [-udc [-f fields] [-s chars] [input_file [output_file]]

DESCRIPTION

uniq reads the input text file input_file, comparing adjacent lines, and copies the result to output_file. If input_file is not specified, the standard input and standard output are used. If input_file is specified, but output_file is not, results are printed to standard output. input_file and output_file must not be the same file.

Line-Comparison Options

uniq recognizes the following options when comparing adjacent lines:

-u: Print only those lines that 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.

If none of the options u, d, or c are present, uniq prints the results of the union of the -u and -d options, producing a copy of the original input file with the second and succeeding copies of any repeated lines removed. (Note that repeated lines must be adjacent in order to be found — see sort(1)).

Field-Skip Options

Two options are provided for skipping an initial portion of each line when making comparisons:

-f fields: Ignore the first fields fields, together with any blanks before each. fields is a positive decimal integer. A field is defined as a string of non-space, non-tab characters separated by tabs and/or spaces from its neighbors.
-s chars: Ignore the first chars characters. chars is a positive decimal integer. Each line in the input is assumed to be terminated with a new line character for purposes of comparison. Fields are skipped before characters.

EXTERNAL INFLUENCES

Environment Variables

LC_COLLATE must be equal to the value it had when the input files were sorted.

LC_CTYPE determines the interpretation of text within files as single- and/or multi-byte characters, and defines a space character when the -f or -s option is used.

LC_MESSAGES determines the language in which messages are displayed.

If LC_COLLATE, LC_CTYPE or LC_MESSAGES is not specified in the environment or is set to the empty string, the value of LANG is used as a default for each unspecified or empty variable. If LANG is not specified or is set to the empty string, a default of "C" (see lang(5)) is used instead of LANG. If any internationalization variable contains an invalid setting, uniq behaves as if all internationalization variables are set to "C". See environ(5).

International Code Set Support

Single- and multi-byte character code sets are supported.

RETURN VALUE

Exit values are:

0: Successful completion.
>0: Error condition occurred.

AUTHOR

uniq was developed by OSF and HP.

STANDARDS CONFORMANCE

uniq: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2