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UNIQ(1P)                   POSIX Programmer's Manual                  UNIQ(1P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

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

SYNOPSIS
       uniq [-c|-d|-u][-f fields][-s char][input_file [output_file]]

DESCRIPTION
       The  uniq  utility  shall read an input file comparing adjacent lines, and write one copy of each input line on
       the output.  The second and succeeding copies of repeated adjacent input lines shall not be written.

       Repeated lines in the input shall not be detected if they are not adjacent.

OPTIONS
       The uniq utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001,  Section  12.2,  Utility
       Syntax Guidelines.

       The following options shall be supported:

       -c     Precede each output line with a count of the number of times the line occurred in the input.

       -d     Suppress the writing of lines that are not repeated in the input.

       -f  fields
              Ignore  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 option-argument specifies more fields than appear on an input line, a null string shall  be  used
       for comparison.

       -s  chars
              Ignore  the first chars characters when doing comparisons, where chars shall be a positive decimal inte-
              ger. If specified in conjunction with the -f option, the first chars characters after the  first  fields
              fields  shall be ignored. If the chars option-argument specifies more characters than remain on an input
              line, a null string shall be used for comparison.

       -u     Suppress the writing of lines that are repeated in the input.


OPERANDS
       The following operands shall be supported:

       input_file
              A pathname of the input file. If the input_file operand is not specified, or if the input_file  is  '-',
              the standard input shall be used.

       output_file
              A pathname of the output file. If the output_file operand is not specified, the standard output shall be
              used. The results are unspecified if the file named by output_file is the file named by input_file.


STDIN
       The standard input shall be used only if no input_file operand is specified or if input_file is '-' .  See  the
       INPUT FILES section.

INPUT FILES
       The input file shall be a text file.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of uniq:

       LANG   Provide  a  default  value  for the internationalization variables that are unset or null. (See the Base
              Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for  the  prece-
              dence of internationalization variables used to determine the values of locale categories.)

       LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables.

       LC_COLLATE

              Determine the locale for ordering rules.

       LC_CTYPE
              Determine the locale for the interpretation of sequences of bytes of text data as characters (for  exam-
              ple,  single-byte as opposed to multi-byte characters in arguments and input files) and which characters
              constitute a <blank> in the current locale.

       LC_MESSAGES
              Determine the locale that should be used to affect the format and contents of diagnostic messages  writ-
              ten to standard error.

       NLSPATH
              Determine the location of message catalogs for the processing of LC_MESSAGES .


ASYNCHRONOUS EVENTS
       Default.

STDOUT
       The standard output shall be used only if no output_file operand is specified. See the OUTPUT FILES section.

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       If the -c option is specified, the output file shall be empty or each line shall be of the form:


              "%d %s", <number of duplicates>, <line>

       otherwise, the output file shall be empty or each line shall be of the form:


              "%s", <line>

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

        0     The utility executed successfully.

       >0     An error occurred.


CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       The sort utility can be used to cause repeated lines to be adjacent in the input file.

EXAMPLES
       The following input file data (but flushed left) was used for a test series on uniq:


              #01 foo0 bar0 foo1 bar1
              #02 bar0 foo1 bar1 foo1
              #03 foo0 bar0 foo1 bar1
              #04
              #05 foo0 bar0 foo1 bar1
              #06 foo0 bar0 foo1 bar1
              #07 bar0 foo1 bar1 foo0

       What follows is a series of test invocations of the uniq utility that use a mixture of uniq options against the
       input file data. These tests verify the meaning of adjacent.  The uniq  utility  views  the  input  data  as  a
       sequence  of  strings delimited by '\n' . Accordingly, for the fieldsth member of the sequence, uniq interprets
       unique or repeated adjacent lines strictly relative to the fields+1th member.

        1. This first example tests the line counting option, comparing each line of the input file data starting from
           the second field:


           uniq -c -f 1 uniq_0I.t
               1 #01 foo0 bar0 foo1 bar1
               1 #02 bar0 foo1 bar1 foo0
               1 #03 foo0 bar0 foo1 bar1
               1 #04
               2 #05 foo0 bar0 foo1 bar1
               1 #07 bar0 foo1 bar1 foo0

       The number '2', prefixing the fifth line of output, signifies that the uniq utility detected a pair of repeated
       lines. Given the input data, this can only be true when uniq is run using the -f 1 option  (which  shall  cause
       uniq to ignore the first field on each input line).


        2. The  second  example  tests the option to suppress unique lines, comparing each line of the input file data
           starting from the second field:


           uniq -d -f 1 uniq_0I.t
           #05 foo0 bar0 foo1 bar1


        3. This test suppresses repeated lines, comparing each line of the input file data starting  from  the  second
           field:


           uniq -u -f 1 uniq_0I.t
           #01 foo0 bar0 foo1 bar1
           #02 bar0 foo1 bar1 foo1
           #03 foo0 bar0 foo1 bar1
           #04
           #07 bar0 foo1 bar1 foo0


        4. This suppresses unique lines, comparing each line of the input file data starting from the third character:


           uniq -d -s 2 uniq_0I.t

       In the last example, the uniq utility found no input matching the above criteria.


RATIONALE
       Some historical implementations have limited lines to be 1080 bytes in length, which does not meet the  implied
       {LINE_MAX} limit.

FUTURE DIRECTIONS
       None.

SEE ALSO
       comm, sort

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  Issue  6,  Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The
       Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Stan-
       dard,  the  original  IEEE  and  The  Open Group Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003                             UNIQ(1P)