Cut (Unix)

cut is a shell command that extracts sections from each line of input text — usually from a file. Extraction of line segments can typically be done by bytes (-b), characters (-c), or fields (-f) separated by a delimiter (-d — the tab character by default). A range must be provided in each case which consists of one of N, N-M, N- (N to the end of the line), or -M (beginning of the line to M), where N and M are counted from 1 (there is no zeroth value). Since version 6, an error is thrown if you include a zeroth value. Prior to this the value was ignored and assumed to be 1.

The original Bell Labs version was written by Gottfried W. R. Luderer.¹² The command is part of the X/Open Portability Guide since issue 2 of 1987. It was inherited into the first version of POSIX.1 and the Single Unix Specification.³ It first appeared in AT&T System III UNIX in 1982.⁴

The command is commonly available on Unix and Unix-like operating systems. It is part of the BSD Base System. The version in GNU coreutils was written by David M. Ihnat, David MacKenzie, and Jim Meyering.⁵ The command is available for Windows via UnxUtils.⁶ The command was ported to the IBM i operating system.⁷

The command line consists of options and an optional file path. If no path is specified than standard input will be used.

Options include:

-b

Bytes; a list following -b specifies a range of bytes which will be returned, e.g. cut -b1-66 would return the first 66 bytes of a line. NB If used in conjunction with -n, no multi-byte characters will be split.

-c

Characters; a list following -c specifies a range of characters which will be returned, e.g. cut -c1-66 would return the first 66 characters of a line

-f

Specifies a field list, separated by a delimiter

list

A comma separated or blank separated list of integer denoted fields, incrementally ordered. The - indicator may be supplied as shorthand to allow inclusion of ranges of fields e.g. 4-6 for ranges 4–6 or 5- as shorthand for field 5 to the end, etc.

-n

Used in combination with -b suppresses splits of multi-byte characters

-d

Delimiter; the character immediately following the -d option is the field delimiter for use in conjunction with the -f option; the default delimiter is tab. Space and other characters with special meanings within the context of the shell in use must be enquoted or escaped as necessary.

-s

Bypasses lines which contain no field delimiters when -f is specified, unless otherwise indicated.

Given a file named foo with content:

foo:bar:baz:qux:quux
one:two:three:four:five:six:seven
alpha:beta:gamma:delta:epsilon:zeta:eta:theta:iota:kappa:lambda:mu
the quick brown fox jumps over the lazy dog

To output the fourth through tenth characters of each line:

$ cut -c 4-10 foo
:bar:ba
:two:th
ha:beta
 quick

To output the fifth field through the end of the line of each line using the colon character as the field delimiter:

$ cut -d ":" -f 5- foo
quux
five:six:seven
epsilon:zeta:eta:theta:iota:kappa:lambda:mu
the quick brown fox jumps over the lazy dog

Because the colon is not found in the last line, the entire line is shown.

Option -d specifies a single character delimiter (in the example above it is a colon) which serves as field separator. Option -f which specifies range of fields included in the output (here fields range from five till the end). Option -d presupposes usage of option -f.

To output the third field of each line using space as the field delimiter:

$ cut -d " " -f 3 foo
foo:bar:baz:qux:quux
one:two:three:four:five:six:seven
alpha:beta:gamma:delta:epsilon:zeta:eta:theta:iota:kappa:lambda:mu
brown

Because the space character is not found in the first three lines these entire lines are shown.

To separate two words having any delimiter:

$ line=process.processid
$ cut -d "." -f1 <<< $line
process
$ cut -d "." -f2 <<< $line
processid