Sed and awk

First, SED (stream editor based on line)

1.1 Basic usage

SED does not edit the source file by default and only handles the data in the pattern space

Sed ' addresscommand ' file ...

Address representation Method:

1. Start and End lines

Example: 1,100 indicates the first row to 100 rows

2. Usage mode

The/regexp/uses the regular expression pattern. Example:/^root/a line that starts with root

3,/pattern1/,/pattern2/

Refers to the first time the line is matched by the pattern 1 to start, to the 1th time by the pattern 2 match to the end of the line, the middle of all the navigation

4, LineNumber

The specified row, $ represents the last line, $-1 represents the second

5, Startline,+n

Starting from Startline, n rows backward.

Command:

1) d: Delete qualifying rows

For example: sed "1,2d"/etc/fstab Delete the first two lines, after processing is finished, print the pattern space to the screen

Sed ' 3, $d '/etc/fstab

Sed '/^\//d '/etc/fstab displays lines starting with a slash

2) P: Display

Sed '/^\//p '/etc/fstab displays lines that begin with a slash, and the result matches the condition of the display twice

should use

Sed-n '/^\//p '/etc/fstab

3) a \ "string": Adds a row after the matched line, with the contents "string"

Sed-n '/^\//a \# Hello World '/etc/fstab

Add a row after the qualifying line Hello World

Sed-n '/^\//a \# Hello World\n#hello linux '/etc/fstab

Add a row after the qualifying line Hello World

4) I \string : Adds a row before the specified line, with the contents "string"

5) R and file name: Adds the contents of the specified file to the qualifying line

Example:

Sed ' 2r/etc/issue '/etc/fstab

Add the/etc/issue entire file after the second line.

Sed ' 1,2r/etc/issue '/etc/fstab

Add the/etc/issue entire file after line 1th and line 2.

6) W Save the content in the specified range to the specified file.

Sed-n '/oot/w/tmp/oot.txt '/etc/fstab

Store rows containing oot in the/etc/fstab to Oot.txt

7) s/pattern/string/modifier: Find and replace. The three slashes can be delimited with any character, such as [email protected]@@

Example

Sed ' s/oot/oot/'/etc/fstab find oot replaced with uppercase OT

Sed ' s/^\//#/'/etc/fstab replaces the slash at the beginning of the line with #

If you do not qualify the beginning of the line, only the string that is matched to the pattern for the first time in each row is replaced

Add modifier

g: Global substitution , just find replacement

Example sed ' s/\//#/g '/etc/fstab global replacement

I: Ignore case when finding

The grep latter reference is enclosed in front, followed by a \1, \2,\ number to refer to

Create file Test.txt, write content

Hello,like

Hi,my Love

Sed ' s#l. E#l. Er#g ' test.txt execution did not achieve the expected result because the latter does not support regular expressions

Sed ' s#l. E#&r#g ' Test.txt & can support latter reference

Hard-latter references use backslashes to escape parentheses

Sed ' s#\ (L.. e\) #\1r#g ' Test.txt

Using only the part of the previous match, you can only use latter to reference the

Change the like into like

To change love into love

Sed ' s#l\ (.. e\) #L \1#g ' Test.txt

Options

-N: Silent mode, does not display in mode space. It's only about the command.

-I : direct modification of source files with caution

-e script-e script: Each followed by a set of scripts, using multiple

-f/path/to/sed_script:

Sed-f/path/to/script File

-R: Allow extended regular expressions to be used

Example:

History | Sed ' s#^[[:space:]]*# #g '

===========================================

1. Remove whitespace characters from the beginning of the/etc/grub.conf file

2. Replace the number in the "Id:3:initdefault:" line in the/etc/inittab file with 5

3. Delete whitespace characters from the/etc/inittab file

4. Delete the # number at the beginning of the/etc/inittab file

4. Remove the # and the trailing white space characters from the beginning of the/etc/inittab file, #号后面有空白字符的才可以删

4. Delete white space characters and # (#前面的空白字符) in the line of a class with white space characters in a file.

5. Remove the directory name of a file path. For example:

/etc/rc.d

/var/log

echo "/ETC/RC.D" | Sed

Second, awk

2.1 Basic Usage

Sed and awk