Master the Linux cut Command: Extract Text Columns Like a Pro

Linux command cut is used for text processing. You can use this command to extract parts of text from a file by selecting columns.

This article provides practical examples of the cut command that can be used in everyday command-line activities.

For most examples we will use the following test file.

$ 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.

1. Selecting character columns

To extract only the desired columns from a file, use the -c option. The following example shows the second character of each line in test.txt.

$ cut -c2 test.txt
a
p
s

As shown, the characters a, p, s are the second characters of each line in test.txt.

2. Selecting a range of characters

By specifying a start and end position separated by a dash, you can also extract a range of characters. The following example extracts the first three characters of each line in test.txt.

$ cut -c1-3 test.txt
cat
cp
ls

3. Selecting characters with a start or end position

You can pass a start or end position to cut using the -c option.

The following specifies only the start position before the dash. This example extracts from the third character to the end of each line.

$ 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.

The following specifies only the end position after the dash. This example extracts the first 8 characters of each line.

$ cut -c-8 test.txt
cat comm
cp comma
ls comma

If you do not specify a number before or after the dash, the whole line is printed, as shown.

$ 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.

4. Selecting specific fields from a file

If you want to extract whole fields instead of a certain number of characters, combine the -f and -d options. -f specifies the fields to extract, and -d specifies the field delimiter used in the input file.

The following example uses ':' as the delimiter to display only the first field of each line in /etc/passwd, which is the username.

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

5. Selecting multiple fields from a file

You can also extract multiple fields from a file or standard output. The example below shows the usernames and home directories of users whose login shell is /bin/bash.

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

To display a range of fields, specify the start and end fields as shown. In this example we select fields 1 to 4, 6 and 7.

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

6. Selecting fields only when a line contains the delimiter

In our /etc/passwd example, if you specify a delimiter other than ':' (colon), cut will display the whole line even if it does not contain the delimiter.

In the following example we set the delimiter to '|' (pipe), and cut shows the whole line because no line contains '|'.

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

However, you can use the -s option to filter and display only lines that contain the specified delimiter.

The following example shows no output because cut did not find any lines with '|' as the delimiter in /etc/passwd.

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

7. Selecting all fields except specified ones

To complement the field list, use the --complement option.

The following example shows all fields in /etc/passwd except field 7.

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

8. Changing the output delimiter

By default, the output delimiter is the same as the input delimiter specified with -d.

To change the output delimiter, use the --output-delimiter option. In this example the input delimiter is ':' but the output delimiter is '#'.

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

9. Changing the output delimiter to a newline

In this example each field output by cut is displayed on a separate line. We still use --output-delimiter, but set its value to $'\n' to insert a newline as the delimiter.

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

10. Combining cut with other Unix commands

When combined with the stdout of other Unix commands, cut can be very powerful.

Once you master the basic usage of cut explained above, you can wisely use it to solve many text manipulation needs.

The following example shows how to extract useful information from the output of the ps command. We also demonstrate using grep and sed to filter ps output before feeding it to cut. Here we use the -d and -f options as explained earlier.

$ ps axu | grep python | sed 's/\s\+/ /g' | cut -d' ' -f2,11-
2231 /usr/bin/python /usr/lib/unity-lens-video/unity-lens-video
2311 /usr/bin/python /usr/lib/unity-scope-video-remote/unity-scope-video-remote
2414 /usr/bin/python /usr/lib/ubuntuone-client/ubuntuone-syncdaemon
2463 /usr/bin/python /usr/lib/system-service/system-service-d
3274 grep --color=auto python