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Linux 2.6 - man page for uniq (linux section 1posix)

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

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 integer. 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, Inter-
	      nationalization Variables for the precedence 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 interna-
	      tionalization 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	example, single-byte as opposed to multi-byte characters in argu-
	      ments 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 diag-
	      nostic messages written 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'  .  Accord-
       ingly,  for  the fieldsth member of the sequence, uniq interprets unique or repeated adja-
       cent 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 start-
	   ing 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,	Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications 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
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					  UNIQ(P)


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