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This article is to share with you about how to use sed, the editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

By default, Sed does not modify the source file directly, but copies it through pipes or file reads to a buffer called the pattern space, where the instructions are completed and printed to the screen.

Syntax format:

It is mentioned above that the positioning is at the end of the line, so the line temporarily defines it as the address, that is, the operation object.

The range of addresses has the following centralized format

N # specify a unique line number

1'2 # specifies to start at line 1 with an interval of 2, that is,

$# specify the last line

/ regular expression / # matches the Operand of the regular expression

\ a regular expression a # matches the regular expression between\ an and a

3 # 5 # match 3-5 lines

1 match 10 # 1 and 10 lines after 1

Options for using sed

Sed [options] [script instructions] [input file]

Option:-n # silent output, does not print the contents of the mode space, and automatically prints by default

-e script # allows multiple script instructions to be executed

-f # read instructions from a file

-the line length of the l # output

-r # extended regular expression

-I # modify the source file directly

Instruction: a (append) # append

D (delete) # Delete

S (substitution) # replace

C # change

Y # replace by character

P # print

Q # exit

I # insert

L # print (display non-print characters)

L # print (display print characters)

R # read the contents of the file

Let's find a file and manipulate it.

Example: append "This is an example" after the first line

[root@pan-S~] # sed "1a This is an example" / opt/fstab_Mrpan

Example: add "This isa example" before line 6 # Note that the source file has changed

[root@pan-S~] # sed-I "6i This is an example" / opt/fstab_Mrpan

Example: replace command

[root@pan-S~] # sed "s/defaults/Mr.pan/g" / opt/fstab_Mrpan

[root@pan-S~] # sed-I "3s/fstab/fstab_Mr.pan/g" / opt/fstab_Mrpan

Example: change command

[root@pan-S~] # sed "/ pan/c exit" / etc/passwd | more

Example: using regular expressions

Match the line units that contain fstab

[root@pan-S~] # sed-I "/ fstab/a This is an example" / opt/fstab_Mrpan

[root@pan-S~] # sed-n "/ ^ $/ d" / opt/fstab_Mrpan

You can use-e-f or a delimiter semicolon when you need to execute multiple instructions; you can also use a branch, but it's best to use the-f file so that it's easy to modify and not error-prone.

Example: delete the line containing example and replace all zeros with 1

(1) # sed-e "/ example/d"-e "s swap 0UniUnix g" / opt/fstab_Mrpan

(2) # sed "/ example/d;s/0/1/g" / opt/fstab_Mrpan

All right, you can operate it yourself and see what's changed.

The above is how to use sed, the editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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