Linux commands for viewing the contents of a file

Linux commands for viewing the contents of a file

Watch the contents of the archive: Cat, TAC, more, less, head, tail, NL, just what we mentioned just to show the appearance of the file, or to move and copy a file or directory, so what if we want to inspect the contents of an archive?! There are quite a few interesting instructions to share: the most commonly used instructions for displaying the contents of a file can be said to be cat and more and less! Also, if we want to look at a very large file (hundreds of MB), but we only need a few lines back-end, then what is the good? Oh! With tail ah, in addition, TAC This command can also be achieved! All right, let's talk about the purpose of each instruction! Cat starts displaying the contents of the archive from the first line the TAC starts with the last line, and you can see that the TAC is the cat's backwards write! More page by page The content of the file is less similar to more, but better than more, he can page forward! Head only a few lines tail only look at the tail a few lines NL display time, by the output line number! OD reads the file in binary mode ...

Abstract: This article describes several common file content viewing tools, such as cat, more, less, head, tail, etc., the most commonly used parameters of these tools, action introduced to the novice, can let the novice in just a few minutes to use. This article is dedicated to the helpless brothers facing the black console.

Directory

1, Cat display file connection file content tool;

1.0 CAT grammatical structure;

1.1 Cat View File content instance;

1.2 Cat's creation, connection file function instance;

2, more file content or output viewing tools;

2.1 More syntax, parameters and action commands;

2.2 More parameter application example;

2.3 More action instructions;

2.4 Other commands by means of pipe and more combined use examples;

3, less view file content tool;

3.1 less syntax format;

3.2 Less's action command;

4, head tool, display the first few lines of file content;

5, tail tool, display the last few lines of file content;

6, about this article;

7, PostScript;

8, reference documents;

9, related documents;

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1, Cat display file connection file content tool;

Cat is a text file viewing and linking tool. To view the contents of a file, it is simpler to use cat, which is the name of the cat directly behind it.

Like what:

[Root@localhost ~]# Cat/etc/fstab

In order to facilitate the novice brother to grasp the tool flexibly, we say a little more commonly used parameters;

1.0 CAT grammatical structure;

Cat [Options] [file] ...

Options

-A,--show-all equivalent to-vet

-B,--number-nonblank number of non-null output lines

-e equivalent to-ve

-E,--show-ends displays at the end of each line

-N,--number all line numbers for the output

-S,--squeeze-blank does not output multiple lines of blank lines

-T vs.-VT equivalence

-T,--show-tabs to display the ^i character as a

-U (ignored)

-V,--show-nonprinting uses ^ and M-references, except LFD and TAB

--HELP Display this help message and leave

1.1 Cat View File content instance;

[Root@localhost ~]# cat/etc/profile Note: View the contents of the profile under the/etc/directory;

[Root@localhost ~]# cat-b/etc/fstab Note: View the contents of the/etc/directory, and number of non-blank lines, line numbers starting from 1;

[Root@localhost ~]# cat-n/etc/profile Note: A numbered output display of all rows (including blank lines) of the profile in/etc directory;

[Root@localhost ~]# cat-e/etc/profile Note: View the profile content under/etc/and append the $ symbol at the end of each line;

Cat plus parameter-N and NL tools, file content output at the same time, each line will be preceded by a line number;

[Email protected] ~]# cat-n/etc/profile

[Email protected] ~]# Nl/etc/profile

Cat can display the contents of multiple files at the same time, for example, we can display the contents of two files simultaneously on a cat command;

[Email protected] ~]# Cat/etc/fstab/etc/profile

For files with great content, cat can be routed through the pipeline | To more tools, and then to a page-by-page view;

[Email protected] ~]# Cat/etc/fstab/etc/profile | More

1.2 Cat's creation, connection file function instance;

Cat has the ability to create files, after creating the file, to end with EOF or stop;

[[email protected] ~]# cat > Linuxsir.org.txt << EOF Note: Create Linuxsir.org.txt file;

> I'll test the cat creation file and enter content for the file; Note: This is for the linuxsir.org.txt file input;

> North-South Test; Note: This is for the Linuxsir.org.txt file input content;

> EOF Note: Exit Edit status;

[email protected] ~]# Cat Linuxsir.org.txt Note: We look at the contents of the Linuxsir.org.txt file;

Let me test the cat creation file and enter the content for the file;

North-South south-north test;

Cat also has the ability to append content to existing files;

[email protected] ~]# Cat Linuxsir.txt Note: View the existing file Linuxsir.txt content;

I am Beinannanbei from linuxsir.org. Note: The content line

I am writing a document for the cat command

[email protected] ~]# cat >> linuxsir.txt << EOF Note: We append content to the Linuxsir.txt file;

> I'll test the cat's ability to append content to the document; Note: This is the content of the recovery

> OK?

> ok~

> North South

> EOF Note: Exit with EOF;

[email protected] ~]# cat linuxsir.txt Note: Check the contents of the file to see if the recovery was successful.

I am Beinannanbei from linuxsir.org.

I am writing a document for the cat command

Let me test cat's ability to append content to a document;

Ok?

ok~

North and South

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

Suppose we have sir01.txt, Sir02.tx and Sir03.txt, and the contents are as follows;

[email protected] ~]# cat Sir01.txt

123456

I am testing

[email protected] ~]# cat Sir02.txt

56789

Beinan tested

[email protected] ~]# cat Sir03.txt

09876

linuxsir.org Testing

I want to connect the Sir01.txt, Sir02.txt, and sir03.txt three files through cat (that is, the contents of the three files together) and output to a new file sir04.txt.

Note: The principle is to connect the contents of three files, then create a sir04.txt file and write the contents of several files to Sir04.txt. In particular, if you enter an existing Sir04.txt file, the Sir04.txt content will be emptied.

[email protected] ~]# cat sir01.txt sir02.txt sir03.txt > Sir04.txt

[Email protected] ~]# more Sir04.txt

123456

I am testing

56789

Beinan tested

09876

linuxsir.org Testing

Cat appends one or more existing file contents to an existing file

[email protected] ~]# cat Sir00.txt

Linuxsir.org Forever

[email protected] ~]# cat sir01.txt sir02.txt sir03.txt >> sir00.txt

[email protected] ~]# cat Sir00.txt

Linuxsir.org Forever

123456

I am testing

56789

Beinan tested

09876

linuxsir.org Testing

Warning: We want to know that > means to create,>> is append. Don't get mixed up. It is not a joke to make a mistake;

2, more file content or output viewing tools;

More is one of our most commonly used tools, the most commonly used is to display the content of the output, and then according to the size of the window to display the page, and then can also indicate the percentage of the file;

[Email protected] ~]# More/etc/profile

2.1 More syntax, parameters and commands;

More [parameter options] [file]

The parameters are as follows:

+num starting from Num line;

-num defines the screen size for NUM lines;

+/pattern starts from the first two lines of the pattern;

-C clear the screen from the top and then display;

-D Prompt Press space to continue, ' Q ' to quit. (Pressing the SPACEBAR to continue, press the Q key to exit), disable the ringing function;

-L ignores Ctrl+l (page break) characters;

-P pages are changed by clearing the window instead of scrolling. A bit similar to the-c parameter;

-S displays consecutive empty lines as one line;

-U Remove the underline from the contents of the file

The action command to exit more is Q

2.2 More parameter application example;

[[email protected] ~]# More-dc/etc/profile Note: Display the prompt and display from the terminal or the top of the console;

[Email protected] ~]# more +4/etc/profile Note: Starting from the 4th line of profile;

[[email protected] ~]# more-4/etc/profile Note: 4 rows per screen;

[Email protected] ~]# more +/mail/etc/profile Note: Start with the first two lines in profile;

2.3 More action instructions;

When we look at a larger file, we use more action instructions, such as ctrl+f (or SPACEBAR) is to display a screen down, Ctrl+b is to return to the previous screen, the ENTER key can scroll down to display n rows, to pass the default is 1 rows;

We only talk about a few commonly used, and try to know it by ourselves;

Enter down n rows, need to be defined, default to 1 rows;

CTRL+F scroll down one screen;

The space bar scrolls down one screen;

Ctrl+b return to the previous screen;

= Output the line number of the current line;

: F output File name and line number of the current line;

V Call VI Editor;

! command to invoke the shell and execute the command;

Q Exit More

When we look at a file, want to call VI to edit it, do not forget the V-action command, which is more convenient;

2.4 Other commands by means of pipe and more combined use examples;

For example, we list a directory of files, because the content is too much, we should learn to use more to page display. This has to do with plumbing | Together, for example:

[Email protected] ~]# ls-l/etc |more

3, less view file content tool;

The less tool is also a tool for paging through files or other output, which is a very powerful tool for Linux to view the contents of a file, and it is a beginner, I suggest you use less. Because less content too much, we put the most commonly used to introduce;

3.1 less syntax format;

Less [parameter] file

Common parameters

-C refreshes the screen from top to bottom and displays the contents of the file. Instead of scrolling through the bottom to complete the refresh;

-F Force open file, binary file display, do not prompt warning;

-I ignores case when searching, unless the search string contains uppercase letters;

-I ignores case when searching, unless the search string contains lowercase letters;

-m displays the percentage of files read;

-m explicit read the file percentage, line number and total number of rows;

-N Enter the travel number in front of each line;

-P Pattern Search pattern, for example, in/etc/profile search word MAIL, use less-p mail/etc/profile

-S displays consecutive blank lines as a blank line;

-Q does not ring under the terminal;

For example: When we display the content of/etc/profile, let it display the line number;

[Email protected] ~]# less-n/etc/profile

3.2 Less's action command;

After entering less, we have to learn a few actions, so that it is more convenient for us to check the contents of the file, the most should remember the command is Q, which allows less to terminate the view file exit;

Action

The ENTER key moves down one line;

Y move up one line;

The space bar scrolls down one screen;

b scroll up one screen;

D scroll down half screen;

H less's help;

U move up the half screen;

W can specify which line to start displaying, which is displayed from the next line of the specified number, for example, 6, which is displayed from line 7th;

G jumps to the first line;

G jumps to the last line;

P n% jumps to n%, such as 10%, which means that it starts at 10% of the entire file content;

/pattern searches for pattern, such as/mail, to search for mail words in a file;

V Call VI Editor;

Q Exit Less

!command Call the shell, you can run the command, such as!ls display the current column in the current directory of all files;

As far as less is concerned, there is too much content, and it is best to look for man when using it. Here is not an example;

4, head tool, display the first few lines of file content;

Head is the number of lines that appear before the contents of a file;

The usage is relatively simple;

Head-n the value file name of the row;

For example, we show the first 10 lines of/etc/profile, which should be:

[Email protected] ~]# head-n 10/etc/profile

5, tail tool, display the last few lines of file content;

Tail is the number of lines that are displayed before the contents of a file;

The usage is relatively simple;

Tail-n the value file name of the row;

For example, we show the last 5 lines of/etc/profile, which should be:

[Email protected] ~]# tail-n 5/etc/profile

6, about this article;

7, PostScript;

8, reference documents;

9, related documents;

"Understanding of paths in Linux file systems"

List, delete, copy, move and rename Linux file and directory management

"Linux file type and file extension"

"Brief description of the directory structure of Linux file system"

Overview of the Linux user and user groups (group) management

The properties of the Linux files and directories

Linux commands for viewing the contents of a file