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uniq(1) General Commands Manual uniq(1) NAME uniq - Removes or lists repeated lines in a file SYNOPSIS Current Syntax uniq [-cdu] [-f fields] [-s chars] [input-file[output-file]] Obsolescent Syntax uniq [-cdu] [-fields] [+chars] [input-file[output-file]] The uniq command reads from the specified input_file, compares adjacent lines, removes the second and succeeding occurrences of a line, and writes to standard output. STANDARDS Interfaces documented on this reference page conform to industry stan- dards as follows: uniq: XPG4, XPG4-UNIX Refer to the standards(5) reference page for more information about in- dustry standards and associated tags. OPTIONS Precedes each output line with a count of the number of times each line appears in the file. This option supersedes the -d and -u options. Displays repeated lines only. Ignores the first fields fields on each input line when doing comparisons, where fields is a positive decimal integer. A field is the maximal string matched by the basic regular expression: [[:blank:]]*[^[:blank:]]* If the fields argument specifies more fields than appear on an input line, a null string is used for comparisons. Ignores the specified number of characters when doing comparisons. The chars argument is a positive decimal integer. If specified with the -f option, the first chars characters af- ter the first fields fields are ignored. If the chars argument specifies more characters than remain on an input line, uniq uses a null string for comparison. Displays unique lines only. Equivalent to -f fields. (Obsolescent) Equivalent to -s chars. (Obsolescent) OPERANDS A pathname for the input file. If this operand is omitted or specified as -, then standard in- put is read. A pathname for the output file. If this operand is omitted, then standard output is written. DESCRIPTION The input_file and output_file arguments must be different files. If the input_file operand is not specified, or if it is -, uniq uses stan- dard input. Repeated lines must be on consecutive lines to be found. You can arrange them with the sort command before processing. EXAMPLES To delete repeated lines in the following file called fruit and save it to a file named newfruit, enter: uniq fruit newfruit The file fruit contains the following lines: apples apples bananas cherries cherries peaches pears The file newfruit contains the following lines: apples bananas cherries peaches pears EXIT STATUS The following exit values are returned: Successful completion. An er- ror occurred. ENVIRONMENT VARIABLES The following environment variables affect the execution of uniq: Pro- vides a default value for the internationalization variables that are unset or null. If LANG is unset or null, the corresponding value from the default locale is used. If any of the internationalization vari- ables contain an invalid setting, the utility behaves as if none of the variables had been defined. If set to a non-empty string value, over- rides the values of all the other internationalization variables. De- termines the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi- byte characters in arguments). Determines the locale for the format and contents of diagnostic messages written to standard error. Deter- mines the location of message catalogues for the processing of LC_MES- SAGES. SEE ALSO Commands: comm(1), sort(1) Standards: standards(5) uniq(1)