CUT(1P) POSIX Programmer's Manual CUT(1P)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.1‐2008, 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 rep‐
resents 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 charac‐
ters 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 charac‐
ter, 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 num‐
ber) 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 speci‐
fied, 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 speci‐
fied, 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 vari‐
ables that are unset or null. (See the Base Definitions vol‐
ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
ables 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 charac‐
ter 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.1‐2008 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 spe‐
cially.
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.1‐2008, 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 delib‐
erately 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 out‐
put.
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 writ‐
ten 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.1‐2008, 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, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
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IEEE/The Open Group 2013 CUT(1P)
