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.
The cut utility shall conform to the Base Definitions volume
of IEEE Std 1003.1-2001, 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 ( low- high), which
represents all fields from the first number to the second
number. The second is a positive number preceded by a hyphen (- high),
which represents all fields from field number 1 to
that number. The third is a positive number followed by a hyphen (
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-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.
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
IEEE Std 1003.1-2001, 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
.
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:
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.)
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 IEEE Std 1003.1-2001 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:
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:
Some historical implementations do not count <backspace>s 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>s or <tab>s 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
IEEE Std 1003.1-2001, 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 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.
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .
IEEE/The Open Group
CUT (P)
2003
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