JIYIK CN >

The cut command belongs to the pipeline command family. Cut is an extraction command that extracts the data we want after analyzing a piece of data. Generally, information is extracted line by line. The meaning of cut is to cut. Yes, the purpose of this command is to cut out a piece of information. The information it processes is in lines. Let's take a look at the usage of the cut command.

# cut [options]…

We will explain the options of the cut command in groups.

Option 1

-d: followed by a separator character. Used to determine which character to use to separate a line of data.
-f: Split a piece of information into several segments based on the separator of -d. Use this option to specify which segment to extract.

Note: 1. –d and –f must be used together, otherwise the command will not be executed correctly;

2. The characters following –f can be divided into several situations

N selects the Nth segment of data to output, and starts counting from 1;
N- starts from the Nth segment of data to the last segment;
N,M intercepts the data of the N and M fields
NM starts from the Nth segment of data to the Mth segment;
-M starts from the 1st segment to the Mth segment;

Let's look at an example of how to view the different fields of the /etc/ passwd file.

# cat /etc/passwd | cut –d ':' –f 3,5 //Intercept data from the third and fifth fields
# cat /etc/passwd | cut –d ':' –f 3-5 //Intercept data from the third to the fifth fields
# cat /etc/passwd | cut –d ':' –f 3 //Intercept data from the third field
# cat /etc/passwd | cut –d ':' –f 3- //Intercept data from the third field (including the third field)
# cat /etc/passwd | cut –d ':' –f -5 //Intercept data from the first field to the fifth field

Here we explain that when displaying the intercepted data, the data segments are connected by the character specified by -d by default.

0:root
1:bin

We can specify the character for the connection through the option --output-delimiter

# cat /etc/passwd | cut –d ':' –f 3,5 –output-delimiter=';'
0;root
1;bin

There is another option to note: --only-delimited. This means that only lines with the character specified by -d are displayed. What does it mean? That is, we use -d to specify the character '0' as the delimiter, but some data does not have '0'. By default, data without '0' will also be displayed. If we do not want it to be displayed, we can use --only-delimited.

# cat /etc/passwd | wc –l
31 //The file has 31 lines of data.
# cat /etc/passwd | cut –d '0' –f 3,5 | wc –l
31 //The result also has 31 lines, but we check the content of the file and find that some lines do not have '0'.
# cat /etc/passwd | cut –d '0' –f 3,5 –only-delimited | wc –l
10 //The result is only 10 lines left, and these 10 lines of data all contain the data we want, which is '0'.

Option 2

-c intercepts fixed character intervals in char units
-b intercepts fixed byte intervals in byte units
-n This option is used together with -b to indicate that characters that occupy multiple bytes will not be split. For example, if a Chinese character occupies multiple characters, this Chinese character will not be split into multiple bytes for interception.

Note: 1. -b and -c cannot be used at the same time

2. The number specified after -c and –b is the same as that of -f

See the following example

# cat /etc/passwd | cut –c 12- //Take the string after 12 characters
# cat /etc/passwd | cut –bn 12- //Take all the characters after 12 bytes

The main purpose of cut is to decompose the data in the same row. It is most commonly used when analyzing some data or text data.

That’s all we have to say about the usage of cut. I hope this article will be helpful to you.