Linux Basic Tutorial Linux under the Cat command use detailed

The purpose of the cat command is to connect files or standard input and print. This command is commonly used to display the contents of a file, or to connect several files to display, or to read from a standard input and display it, often in conjunction with redirection symbols.

1. Command format:

Cat [Options] [file] ...

2. Command function:

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Small, to talk about the three main features of cat:

1. Display the entire file at once: Cat filename

2. Create a file from the keyboard: cat > FileName can only create new files and cannot edit existing files.

3. Merge several files into one file: Cat file1 file2 > file

3. Command parameters:

-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, numbering the number of rows for all outputs starting from 1

-S,--squeeze-blank a blank line that has more than two lines in a row and is substituted for a row

-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

4. Usage examples:

Example one: Add the Log2012.log file contents to the line number and enter Log2013.log this file

Command:

Cat-n Log2012.loglog2013.log

Output:

Copy Code

The code is as follows:

[Email protected] test]# Catlog2012.log

2012-01

2012-02</p><p>======[[email protected] test]# cat Log2013.log

2013-01

2013-02</p><p>2013-03

======[[email protected]]# cat-n Log2012.log log2013.log

1 2012-01

2 2012-02

3

4

5 ======

6 2013-01

7 2013-02

8

9

10 2013-03

======[[email protected]]#

Description

Example two: Add the contents of the Log2012.log and Log2013.log files to the log.log after adding the line number (blank line).

Command:

Cat-b Log2012.loglog2013.log Log.log

Output:

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The code is as follows:

[Email protected] test]# cat-b log2012.log log2013.log log.log

1 2012-01

2 2012-02

3 ======

4 2013-01

5 2013-02

6 2013-03

7 ======[[email protected]]#

Example three: Add the Log2012.log file contents to the line number after the input log.log this file

Command:

Output:

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The code is as follows:

[Email protected] test]# Catlog.log

[Email protected] test]# cat-n log2012.log > Log.log

[Email protected] test]# cat-n log.log

1 2012-01

2 2012-02

3

4

5 ======

[Email protected] test]#

Example four: Using here doc to generate files

Output:

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The code is as follows:

[Email protected] test]# Cat>log.txt <<eof

> Hello

> World

> Linux

> pwd=$ (PWD)

> EOF

[Email protected] test]# Ls-l Log.txt

-rw-r--r--1 root root 3710-28 17:07 log.txt

[Email protected] test]# Catlog.txt

Hello

World

Linux

Pwd=/opt/soft/test

[Email protected] test]#

Description

Note that the Bold section, here Doc, can be used for string substitution.

Note:

TAC (Reverse list)

Command:

TAC Log.txt

Output:

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The code is as follows:

[Email protected] test]# Taclog.txt

Pwd=/opt/soft/test

Linux

World

Hello

The TAC is writing cat back, so his function is in contrast to cat, which is displayed continuously on the screen from the first line to the last line, while the TAC is displayed on the screen in reverse from the last line to the first line!

Linux Basic Tutorial Linux under the Cat command use detailed