Master the Linux ‘cut’ Command: Practical Examples and Advanced Options

Introduction

The cut command extracts selected portions of each line from a file or standard input, using bytes, characters, or fields separated by a delimiter. It is a fundamental tool for text processing in Linux and Unix environments.

Basic Syntax

$ cut OPTION... [FILE]...

Common Options

-f

: extract specified fields; the default delimiter is a Tab. -d: define a custom delimiter instead of the default Tab. -b: extract specified bytes; ranges can be given with a hyphen. -c: extract specified characters; accepts comma‑separated lists or hyphen‑separated ranges. --complement: output all fields except those selected (inverse selection). --output-delimiter: set a different delimiter for the output. --only-delimited: suppress lines that do not contain the delimiter.

Sample Files

Two example files are used throughout the examples:

$ cat content.txt
Ubuntu Linux
Microsoft Windows
OsX El Capitan
Unix
FreeBSD

# /etc/passwd (excerpt)
root:x:0:0:root:/root:/bin/bash
alvin:x:1000:1000:alvin:/home/alvin:/bin/bash

Examples

Extract the first field of /etc/passwd using a colon as delimiter:

$ cut -d':' -f1 /etc/passwd
root
bin
daemon
adm
lp
sync
shutdown
halt
mail
operator
games
alvin
liangxu
...

Extract the first field of content.txt using a space as delimiter:

$ cut -d " " -f1 content.txt
Ubuntu
Microsoft
OsX
Unix
FreeBSD

Combine fields 1 and 6 from lines containing /bin/bash in /etc/passwd :

$ grep "/bin/bash" /etc/passwd | cut -d':' -f1,6
root:/root
alvin:/home/alvin

Select a range of fields (1‑4,6,7) from /etc/passwd :

$ grep "/bin/bash" /etc/passwd | cut -d':' -f1-4,6,7
root:x:0:0:/root:/bin/bash
alvin:x:1000:1000:/home/alvin:/bin/bash

Use --complement to output all fields except the second one:

$ grep "/bin/bash" /etc/passwd | cut -d':' --complement -f2
root:0:0:root:/root:/bin/bash

Change the output delimiter to a space:

$ cut -d: -f1,7 --output-delimiter ' ' /etc/passwd | sort | uniq -u
_apt /usr/sbin/nologin
backup /usr/sbin/nologin
bin /usr/sbin/nologin
...

Set the output delimiter to a newline (each field on its own line):

$ grep root /etc/passwd | cut -d':' -f1,6,7 --output-delimiter=$'
'
root
/root
/bin/bash

Extract characters by position:

$ cut -c 1 content.txt
U
M
O
U
F

$ cut -c 1-7 content.txt
Ubuntu
Microso
OsX El
Unix
FreeBSD

Extract bytes:

$ cut -b 1,2,3 content.txt
Ubu
Mic
OsX
Uni
Fre

Combine cut with other commands (e.g., ps , free ) for more complex pipelines:

# Extract USER, PID, COMMAND from ps output
ps -L u n | tr -s " " | cut -d " " -f2,3,14-
USER PID COMMAND
0 676 /sbin/agetty -o -p -- \u --keep-baud 115200,38400,9600 ttyS0 vt220
...

# Save total, used, free memory values to a file
free -m | tr -s ' ' | sed '/^Mem/!d' | cut -d" " -f2-4 >> memory.txt
cat memory.txt
985 86 234

Limitations

The cut command cannot specify multiple characters as a delimiter; consecutive spaces are treated as separate delimiters. To handle such cases, preprocess the input with tr or similar tools before using cut.