Cat commands in Linux

Simplified Version:

CAT has three main functions:

1. display the entire file at a time. $ Cat filename

2. Create a file from the keyboard. $ Cat> filename

Only new files can be created, and existing files cannot be edited.

3. Merge several files into one file: $ cat file1 file2> File Parameters:

-N or -- number indicates the number of all output rows starting from 1.

-B or -- number-nonblank is similar to-N, but is not numbered for blank rows.

-S or -- Squeeze-blank when there are two consecutive blank rows or more, it is replaced by a blank row

-V or -- show-nonprinting
Example:

Add the row number to the file content of textfile1 and enter textfile2.

Cat-N textfile1> textfile2
Add the row number to the file content of textfile1 and textfile2 (blank rows are not added) and then append the content to textfile3.

Cat-B textfile1 textfile2> textfile3   Throw the test.txt file into the garbage box and leave the value test.txt empty.
CAT/dev/null>/etc/test.txt      

Details:

Turn: http://blog.sina.com.cn/s/blog_52f6ead0010127xm.html

Cat is a tool for viewing and connecting text files. View the content of a file. It is easy to use cat, that is, the file name is directly followed by CAT.

For example:

De> [root @ localhost ~] # Cat/etc/fstabde>

To make it easier for new students to master this tool flexibly, let's talk about common parameters;

1.0 cat syntax structure;

De> CAT [Option] [file] ...de>

Option
-A, -- show-all is equivalent to-vet.
-B, -- number-nonblank: Number of non-empty output rows
-E is equivalent to-ve.
-E, -- show-ends is displayed at the end of each line $
-N, -- number indicates the number of all rows output.
-S, -- Squeeze-blank does not output multiple empty rows
-T is equivalent to-vt.
-T, -- show-tabs: The jump character is displayed as ^ I
-U (ignored)
-V, -- show-nonprinting use ^ and M-reference, except LFD and Tab
-- Help: displays the help information and leaves

1.1 cat view the file content instance;

De> [root @ localhost ~] # Cat/etc/profile Note: view the profile file content in the/etc/directory;

[Root @ localhost ~] # Cat-B/etc/fstab Note: view the profile content in the/etc/directory and number non-blank rows. The row number starts from 1;

[Root @ localhost ~] # Cat-N/etc/profile Note: Numbers all the rows (including blank rows) of the profile in the/etc directory are output;

[Root @ localhost ~] # Cat-E/etc/profile Note: view the profile content under/etc/and add the $ symbol at the end of each line. De>

The cat parameter-N is similar to the NL tool. When the file content is output, the row number is added before each line;

De> [root @ localhost ~] # Cat-N/etc/profile

[Root @ localhost ~] # NL/etc/profilede>

Cat can display the content of multiple files at the same time. For example, we can display the content of two files at the same time on a cat command;

De> [root @ localhost ~] # Cat/etc/fstab/etc/profilede>

For files with large content, cat can be transferred to the more tool through pipelines and viewed on a page by page;

De> [root @ localhost ~] # Cat/etc/fstab/etc/profile | morede>

1.2 create and connect cat file function instances;

Cat can create files. After creating a file, it must end with EOF or stop;

De> [root @ localhost ~] # Cat> linuxsir.org.txt <EOF Note: Create the linuxsir.org.txt file;

> I will test cat to create a file and input content for the file. Note: This is the input content for the linuxsir.org.txt file;

> North-south-north testing; note: this is the input content of linuxsir.org.txt;

> EOF Note: exit the editing status;


[Root @ localhost ~] # Cat linuxsir.org.txt Note: We recommend the content of the linuxsir.org.txt file;


I will test cat to create a file and input content for the file;

North-south-north testing; de>

CAT also provides the ability to Append content to existing files;

De> [root @ localhost ~] # Cat linuxsir.txt Note: Check the existing file linuxsir.txt content;

I am beinannanbei from linuxsir. org. Note: Content line

I am writing a document for the cat command



[Root @ localhost ~] # Cat> linuxsir.txt <EOF Note: We Append content to the linuxsir.txt file;

> I will test the cat Append content to the document function. Note: This is the retrieved content.

> OK?

> OK ~

> Presented to the North South

> EOF Note: exit with EOF;



[Root @ localhost ~] # Cat linuxsir.txt Note: Check the file content to see if it has been recovered successfully.

I am beinannanbei from linuxsir. org.

I am writing a document for the cat command


Let me test the cat Append content to the document;

OK?

OK ~

North South presents de>

Cat connects the content of multiple files and outputs them to a new file;

Suppose we have sir01.txt1_sir02.txand sir03.txt, And the content is as follows;

De> [root @ localhost ~] # Cat sir01.txt

123456

I am testing


[Root @ localhost ~] # Cat sir02.txt

56789

Beinan tested


[Root @ localhost ~] # Cat sir03.txt

09876

Linuxsir.org testingde>

I want to use Cat to connect the three files sir01.txt1_sir02.txtand sir03.txt together (I also say that the three files are connected together and exported to a new file sir04.txt.

Note: logging is in progress. The special value is that if you input a sir04.txt file that already exists, the sir04.txt content will be cleared.

De> [root @ localhost ~] # Cat sir01.txt sir02.txt sir03.txt> sir04.txt


[Root @ localhost ~] # More sir04.txt

123456

I am testing

56789

Beinan tested

09876

Linuxsir.org testingde>

Cat appends the content of one or more existing files to an existing file.

De> [root @ localhost ~] # Cat sir00.txt

Linuxsir.org forever


[Root @ localhost ~] # Cat sir01.txt sir02.txt sir03.txt> sir00.txt


[Root @ localhost ~] # Cat sir00.txt

Linuxsir.org forever

123456

I am testing

56789

Beinan tested

09876

Linuxsir.org testingde>

Warning: You Need To Know> Create,> append. Never confuse. Making mistakes is not a joke;