sed commands use simple records

Sed ' s/pattern/replace_string/' file

Replace sed ' s/lifeng/lf/' sed.txt with LF for the first lifeng of each line in Sed.txt (the source file content will not change)

To replace all content, command tail plus parameter g sed ' s/lifeng/lf/g' Sed.txt

To match the second content of each line using 2g sed ' s/lifeng/lf/2g' Sed.txt

You can also use Cat Sed.txt | Sed ' s/lifeng/lf/' >file (output redirect)

If you want to directly modify the original file plus parameters –i sed –i ' s/lifeng/lf/' sed.txt

Sed–i. Bak ' s/lifeng/lf/' Sed.txt replaces the source file and creates a File.bak backup file

Sed removal of blank line sed '/^$/d ' sed.txt

blank line available regular ^$     to indicate /pattern/d The row that matches the style will be removed

Matched string token:& indicates matched content

[[email protected] csv]# echo this was an example|sed ' s/\w\+/[&]/g '

[This] [IS] [An] [Example]

[[email protected] csv]# echo this was an example|sed ' s/\w\+/[&]/'

[This] was an example

Regular \w\+ matches each word and then we replace it with [&] & corresponds to the word that was previously matched

Quotes

Sed expressions are generally quoted in single quotes, but they can also be used in double quotes, and double quotation marks can be extended by evaluating an expression, and double quotes are useful when we want to use some variables in an SED expression.

Example: Text=hello

echo Hello word|sed "s/$text/hello/" (single quote not)

HELLO Word

This is to delete the first row to the nth row

Sed-i ' 1,nd ' filename

sed commands use simple records