Mastering Linux cut: 10 Practical Ways to Extract Text Efficiently

Linux command cut is used for text processing, allowing extraction of specific columns from files.

This article provides practical examples of cut usage in everyday command-line activities.

<code>$ cat test.txt
cat command for file oriented operations.
cp command for copy files or directories.
ls command to list out files and directories with its attributes.</code>

1. Select character columns

Use the

-c

option to extract desired columns. The example shows the second character of each line in

test.txt

.

<code>$ cut -c2 test.txt
a
p
s</code>

The output displays the characters

a

,

p

,

s

as the second character of each line.

2. Use range to select character columns

Specify start and end positions with

-c

using a hyphen. The example extracts the first three characters of each line.

<code>$ cut -c1-3 test.txt
cat
cp
ls</code>

3. Use start or end position only

Provide only a start or an end position with

-c

. The first example extracts from the third character to the end of each line.

<code>$ cut -c3- test.txt
t command for file oriented operations.
 command for copy files or directories.
 command to list out files and directories with its attributes.</code>

The second example extracts the first eight characters of each line.

<code>$ cut -c-8 test.txt
cat comm
cp comma
ls comma</code>

If neither start nor end is specified, the whole line is printed.

<code>$ cut -c- test.txt
cat command for file oriented operations.
cp command for copy files or directories.
ls command to list out files and directories with its attributes.</code>

4. Select specific fields

Combine

-f

and

-d

to extract fields separated by a delimiter. The example uses ':' to display the first field (username) from

/etc/passwd

.

<code>$ cut -d':' -f1 /etc/passwd
root
daemon
bin
sys
sync
games
bala</code>

5. Select multiple fields

Extract multiple fields, for example, the username and home directory of users whose login shell is

/bin/bash

.

<code>$ grep "/bin/bash" /etc/passwd | cut -d':' -f1,6
root:x:0:0:root:/root:/bin/bash
bala:x:1000:1000:bala,,,:/home/bala:/bin/bash</code>

6. Select fields only when line contains delimiter

Use the

-s

option to suppress lines that do not contain the specified delimiter.

<code>$ grep "/bin/bash" /etc/passwd | cut -d'|' -s -f1</code>

Since the delimiter '|' does not appear in the file, no output is produced.

7. Complement: select all fields except specified

Use

--complement

to exclude fields; the example shows all fields except field 7.

<code>$ grep "/bin/bash" /etc/passwd | cut -d':' --complement -f7
root:x:0:0:root:/root
bala:x:1000:1000:bala,,,:/home/bala</code>

8. Change output delimiter

By default the output delimiter matches the input delimiter; use

--output-delimiter

to change it, e.g., to '#'.

<code>$ grep "/bin/bash" /etc/passwd | cut -d':' -s -f1,6,7 --output-delimiter='#'
root# /root# /bin/bash
bala# /home/bala# /bin/bash</code>

9. Use newline as output delimiter

Set the output delimiter to a newline with

$'\n'

to print each field on a separate line.

<code>$ grep bala /etc/passwd | cut -d':' -f1,6,7 --output-delimiter=$'\n'
bala
/home/bala
/bin/bash</code>

10. Combine cut with other Unix commands

Cut can be combined with pipelines to process command output, such as extracting useful columns from

ps

output after filtering with

grep

and

sed

.

<code>$ ps axu | grep python | sed 's/\s\+/ /g' | cut -d' ' -f2,11
2231 /usr/bin/python ...
2311 /usr/bin/python ...
2414 /usr/bin/python ...
2463 /usr/bin/python ...
3274 grep --color=auto python</code>