UNIQ(1)                 FreeBSD General Commands Manual                UNIQ(1)

NAME
     uniq - report or filter out repeated lines in a file

SYNOPSIS
     uniq [-c | -d | -D | -u] [-i] [-f num] [-s chars] [input_file
          [output_file]]

DESCRIPTION
     The uniq utility reads the specified input_file comparing adjacent lines,
     and writes a copy of each unique input line to the output_file.  If
     input_file is a single dash (`-') or absent, the standard input is read.
     If output_file is absent, standard output is used for output.  The second
     and succeeding copies of identical adjacent input lines are not written.
     Repeated lines in the input will not be detected if they are not
     adjacent, so it may be necessary to sort the files first.

     The following options are available:

     -c, --count
             Precede each output line with the count of the number of times
             the line occurred in the input, followed by a single space.

     -d, --repeated
             Output a single copy of each line that is repeated in the input.

     -D, --all-repeated [septype]
             Output all lines that are repeated (like -d, but each copy of the
             repeated line is written).  The optional septype argument
             controls how to separate groups of repeated lines in the output;
             it must be one of the following values:

             none      Do not separate groups of lines (this is the default).
             prepend   Output an empty line before each group of lines.
             separate  Output an empty line after each group of lines.

     -f num, --skip-fields num
             Ignore the first num fields in each input line when doing
             comparisons.  A field is a string of non-blank characters
             separated from adjacent fields by blanks.  Field numbers are one
             based, i.e., the first field is field one.

     -i, --ignore-case
             Case insensitive comparison of lines.

     -s chars, --skip-chars chars
             Ignore the first chars characters in each input line when doing
             comparisons.  If specified in conjunction with the -f, --unique
             option, the first chars characters after the first num fields
             will be ignored.  Character numbers are one based, i.e., the
             first character is character one.

     -u, --unique
             Only output lines that are not repeated in the input.

ENVIRONMENT
     The LANG, LC_ALL, LC_COLLATE and LC_CTYPE environment variables affect
     the execution of uniq as described in environ(7).

EXIT STATUS
     The uniq utility exits 0 on success, and >0 if an error occurs.

EXAMPLES
     Assuming a file named cities.txt with the following content:

           Madrid
           Lisbon
           Madrid

     The following command reports three different lines since identical
     elements are not adjacent:

           $ uniq -u cities.txt
           Madrid
           Lisbon
           Madrid

     Sort the file and count the number of identical lines:

           $ sort cities.txt | uniq -c
                   1 Lisbon
                   2 Madrid

     Assuming the following content for the file cities.txt:

           madrid
           Madrid
           Lisbon

     Show repeated lines ignoring case sensitiveness:

           $ uniq -d -i cities.txt
           madrid

     Same as above but showing the whole group of repeated lines:

           $ uniq -D -i cities.txt
           madrid
           Madrid

     Report the number of identical lines ignoring the first character of
     every line:

           $ uniq -s 1 -c cities.txt
                   2 madrid
                   1 Lisbon

COMPATIBILITY
     The historic +number and -number options have been deprecated but are
     still supported in this implementation.

SEE ALSO
     sort(1)

STANDARDS
     The uniq utility conforms to IEEE Std 1003.1-2001 ("POSIX.1") as amended
     by Cor. 1-2002.

HISTORY
     A uniq command appeared in Version 3 AT&T UNIX.

FreeBSD 13.1-RELEASE-p6          June 7, 2020          FreeBSD 13.1-RELEASE-p6