UNIQ(1) BSD Reference Manual UNIQ(1)
uniq - report or filter out repeated lines in a file
uniq [-c | -d | -u] [-f fields] [-s chars] [input_file [output_file]]
The uniq utility reads the standard input comparing adjacent lines, and
writes a copy of each unique input line to the standard output. The sec-
ond and succeeding copies of identical adjacent input lines are not writ-
ten. 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 Don't output lines that are not repeated in the input.
Ignore the first fields in each input line when doing compar-
isons. 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.
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 fields fields will be ig-
nored. Character numbers are one based, i.e. the first character
is character one.
-u Don't output lines that are repeated in the input.
If additional arguments are specified on the command line, the first such
argument is used as the name of an input file, the second is used as the
name of an output file.
The uniq utility exits 0 on success, and >0 if an error occurs.
The historic +number and -number options have been deprecated but are
still supported in this implementation.
The uniq utility is expected to be IEEE Std1003.2 (``POSIX'') compatible.
4.4BSD June 6, 1993 1