— report or
filter out repeated lines in a file
utility reads the standard input comparing
adjacent lines and writes a copy of each unique input line to the standard
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 options are as follows:
- Precede each output line with the count of the number of
times the line occurred in the input, followed by a single space.
- Only output lines which have duplicates.
- Ignore the first fields in
each input line when doing comparisons. A field is a string of non-blank
characters separated from adjacent fields by blanks, with blanks
considered part of the following field. 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 ignored. Character
numbers are one based, i.e., the first character is character one.
- Only output lines which are unique.
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. A file name of ‘
denotes the standard input or the standard output (depending on its position
on the command line).
- The character encoding
locale(1). It decides which
byte sequences form characters and which characters are considered blank.
If unset or set to “C”, “POSIX”, or an
unsupported value, each byte is treated as a character, and only space and
tab are considered blank.
utility exits 0 on success,
and >0 if an error occurs.
utility is compliant with the
IEEE Std 1003.1-2008
The use of -c
in conjunction with
extension to that specification.
have been deprecated but are still supported in this implementation.