Do pipes know when they have to "wait" for all the data? Post: 302412374

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uniq

UNIQ(1) 						    BSD General Commands Manual 						   UNIQ(1)

NAME

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

SYNOPSIS

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

     -d      Only output lines that are repeated in the input.

     -f 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.

     -s chars
	     Ignore the first chars characters in each input line when doing comparisons.  If specified in conjunction with the -f 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      Only output lines that are not repeated in the input.

     -i      Case insensitive comparison of lines.

DIAGNOSTICS

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

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 is expected to be IEEE Std 1003.2 (``POSIX.2'') compatible.

HISTORY

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

BSD
								   June 6, 1993 							       BSD