CUT
Section: POSIX Programmer's Manual (1P)
Updated: 2017
Page Index
PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
NAME
cut
--- cut out selected fields of each line of a file
SYNOPSIS
cut -b list [-n] [file...]
cut -c list [file...]
cut -f list [-d delim] [-s] [file...]
DESCRIPTION
The
cut
utility shall cut out bytes (
-b
option), characters (
-c
option), or character-delimited fields (
-f
option) from each line in one or more files, concatenate them, and
write them to standard output.
OPTIONS
The
cut
utility shall conform to the Base Definitions volume of POSIX.1-2017,
Section 12.2,
Utility Syntax Guidelines.
The application shall ensure that the option-argument
list
(see options
-b,
-c,
and
-f
below) is a
<comma>-separated
list or
<blank>-separated
list of positive numbers and ranges. Ranges can be in three forms. The
first is two positive numbers separated by a
<hyphen-minus>
(low-high),
which represents all fields from the first number to the second
number. The second is a positive number preceded by a
<hyphen-minus>
(-high),
which represents all fields from field number 1 to that number. The
third is a positive number followed by a
<hyphen-minus>
(low-),
which represents that number to the last field, inclusive. The elements
in
list
can be repeated, can overlap, and can be specified in any order, but
the bytes, characters, or fields selected shall be written in the order
of the input data. If an element appears in the selection list more
than once, it shall be written exactly once.
The following options shall be supported:
- -b list
-
Cut based on a
list
of bytes. Each selected byte shall be output unless the
-n
option is also specified. It shall not be an error to select bytes not
present in the input line.
- -c list
-
Cut based on a
list
of characters. Each selected character shall be output. It shall not
be an error to select characters not present in the input line.
- -d delim
-
Set the field delimiter to the character
delim.
The default is the
<tab>.
- -f list
-
Cut based on a
list
of fields, assumed to be separated in the file by a delimiter character
(see
-d).
Each selected field shall be output. Output fields shall be separated
by a single occurrence of the field delimiter character. Lines with no
field delimiters shall be passed through intact, unless
-s
is specified. It shall not be an error to select fields not present in
the input line.
- -n
-
Do not split characters. When specified with the
-b
option, each element in
list
of the form
low-high
(<hyphen-minus>-separated
numbers) shall be modified as follows:
-
- *
-
If the byte selected by
low
is not the first byte of a character,
low
shall be decremented to select the first byte of the character
originally selected by
low.
If the byte selected by
high
is not the last byte of a character,
high
shall be decremented to select the last byte of the character prior to
the character originally selected by
high,
or zero if there is no prior character. If the resulting range element
has
high
equal to zero or
low
greater than
high,
the list element shall be dropped from
list
for that input line without causing an error.
Each element in
list
of the form
low-
shall be treated as above with
high
set to the number of bytes in the current line, not including the
terminating
<newline>.
Each element in
list
of the form -high
shall be treated as above with
low
set to 1. Each element in
list
of the form
num
(a single number) shall be treated as above with
low
set to
num
and
high
set to
num.
- -s
-
Suppress lines with no delimiter characters, when used with the
-f
option. Unless specified, lines with no delimiters shall be passed
through untouched.
OPERANDS
The following operand shall be supported:
- file
-
A pathname of an input file. If no
file
operands are specified, or if a
file
operand is
'-',
the standard input shall be used.
STDIN
The standard input shall be used only if no
file
operands are specified, or if a
file
operand is
'-'.
See the INPUT FILES section.
INPUT FILES
The input files shall be text files, except that line lengths shall be
unlimited.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of
cut:
- LANG
-
Provide a default value for the internationalization variables that are
unset or null. (See the Base Definitions volume of POSIX.1-2017,
Section 8.2, Internationalization 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 internationalization variables.
- 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 arguments and input files).
- LC_MESSAGES
-
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard error.
- NLSPATH
-
Determine the location of message catalogs for the processing of
LC_MESSAGES.
ASYNCHRONOUS EVENTS
Default.
STDOUT
The
cut
utility output shall be a concatenation of the selected bytes,
characters, or fields (one of the following):
-
"%s\n", <concatenation of bytes>
"%s\n", <concatenation of characters>
"%s\n", <concatenation of fields and field delimiters>
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
- 0
-
All input files were output successfully.
- >0
-
An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
The
cut
and
fold
utilities can be used to create text files out of files with
arbitrary line lengths. The
cut
utility should be used when the number of lines (or records) needs
to remain constant. The
fold
utility should be used when the contents of long lines need to be
kept contiguous.
Earlier versions of the
cut
utility worked in an environment where bytes and characters were
considered equivalent (modulo
<backspace>
and
<tab>
processing in some implementations). In the extended world of
multi-byte characters, the new
-b
option has been added. The
-n
option (used with
-b)
allows it to be used to act on bytes rounded to character boundaries.
The algorithm specified for
-n
guarantees that:
-
cut -b 1-500 -n file > file1
cut -b 501- -n file > file2
ends up with all the characters in
file
appearing exactly once in
file1
or
file2.
(There is, however, a
<newline>
in both
file1
and
file2
for each
<newline>
in
file.)
EXAMPLES
Examples of the option qualifier list:
- 1,4,7
-
Select the first, fourth, and seventh bytes, characters, or fields and
field delimiters.
- 1-3,8
-
Equivalent to 1,2,3,8.
- -5,10
-
Equivalent to 1,2,3,4,5,10.
- 3-
-
Equivalent to third to last, inclusive.
The
low-high
forms are not always equivalent when used with
-b
and
-n
and multi-byte characters; see the description of
-n.
The following command:
-
cut -d : -f 1,6 /etc/passwd
reads the System V password file (user database) and produces lines of
the form:
-
<user ID>:<home directory>
Most utilities in this volume of POSIX.1-2017 work on text files. The
cut
utility can be used to turn files with arbitrary line lengths into a
set of text files containing the same data. The
paste
utility can be used to create (or recreate) files with arbitrary line
lengths. For example, if
file
contains long lines:
-
cut -b 1-500 -n file > file1
cut -b 501- -n file > file2
creates
file1
(a text file) with lines no longer than 500 bytes (plus the
<newline>)
and
file2
that contains the remainder of the data from
file.
(Note that
file2
is not a text file if there are lines in
file
that are longer than 500 +
{LINE_MAX}
bytes.) The original file can be recreated from
file1
and
file2
using the command:
-
paste -d "\0" file1 file2 > file
RATIONALE
Some historical implementations do not count
<backspace>
characters in determining character counts with the
-c
option. This may be useful for using
cut
for processing
nroff
output. It was deliberately decided not to have the
-c
option treat either
<backspace>
or
<tab>
characters in any special fashion. The
fold
utility does treat these characters specially.
Unlike other utilities, some historical implementations of
cut
exit after not finding an input file, rather than continuing to process
the remaining
file
operands. This behavior is prohibited by this volume of POSIX.1-2017, where only the exit
status is affected by this problem.
The behavior of
cut
when provided with either mutually-exclusive options or options that do
not work logically together has been deliberately left unspecified in
favor of global wording in
Section 1.4, Utility Description Defaults.
The OPTIONS section was changed in response to IEEE PASC Interpretation
1003.2 #149. The change represents historical practice on all known
systems. The original standard was ambiguous on the nature of the
output.
The
list
option-arguments are historically used to select the portions of the
line to be written, but do not affect the order of the data. For
example:
-
echo abcdefghi | cut -c6,2,4-7,1
yields
"abdefg".
A proposal to enhance
cut
with the following option:
- -o
-
Preserve the selected field order. When this option is specified, each
byte, character, or field (or ranges of such) shall be written in the
order specified by the
list
option-argument, even if this requires multiple outputs of the same
bytes, characters, or fields.
was rejected because this type of enhancement is outside the scope of
the IEEE P1003.2b draft standard.
FUTURE DIRECTIONS
None.
SEE ALSO
Section 2.5,
Parameters and Variables,
fold,
grep,
paste
The Base Definitions volume of POSIX.1-2017,
Chapter 8, Environment Variables,
Section 12.2, Utility Syntax Guidelines
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 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 original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
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https://www.kernel.org/doc/man-pages/reporting_bugs.html .