The
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.
ENVIRONMENT
The
LANGLC_ALLLC_COLLATE
and
LC_CTYPE
environment variables affect the execution of
as described in
environ(7).
EXIT STATUS
Ex -std
COMPATIBILITY
The historic
+ number
and
-number
options have been deprecated but are still supported in this implementation.
