Ubuntu Manpage: cut - cut out selected fields of each line of a file

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 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.

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  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 .

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

       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:

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:

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>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.

FUTURE DIRECTIONS

       None.

COPYRIGHT

       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 .