preface

Sed, full name for Stream Editor, is a stream editor for text processing that supports regular expressions. Sed processes text one line at a time

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Sed grammar

• The sed command processes content in the schema space rather than directly processing file content. If I is added, the content of the file can be modified directly
• Example:Sed -i 's/ original string/new string /' /home/test.txt

Sed [-nefr parameter] [function] [filePath]

• The -n option is set to quiet mode with the -n option, that is, no default print is printed, unless the print p option is specified in the subcommand, only lines that match changes are printed

---- print both lines ---- server11:~/test# echo -e 'hello \n world' | sed 's/hello/csc/'CSC world ---- did not print a line ----- server11:~/test# echo -e 'hello \n world' | sed -n 's/hello/csc/'---- a matching line ----- server11:~/test is printed# echo -e 'hello \n world' | sed -n 's/hello/csc/p'
csc 
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• Option -e, multiple sliver commands operate consecutively

echo -e 'hello world' | sed -e 's/hello/csc/' -e 's/world/lwl/'Results: CSC LWLCopy the code

• The -i option directly modifies the contents of the read file

server11:~/test # cat file.txt 
hello world
server11:~/test # sed 's/hello/lwl/' file.txt 
lwl world
server11:~/test # cat file.txt              Hello world ---- You can modify the file contents by adding the I parameter ---- server11:~/test# sed -i 's/hello/lwl/' file.txt 
lwl world
server11:~/test # cat file.txt              
lwl world
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• The -f option executes the file script

Sed. Script Script content: s/hello/ CSC/s/world/ LWL / ------ echo"hello world"| sed -f sed. Script results: CSC LWLCopy the code

• -r. By default, only basic regular expressions are supported. To support extended regular expressions, -r is required

echo "hello world" | sed -r 's/(hello)|(world)/csc/g'
csc csc
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[n1[,n2]] function or /{pattern}/function

• N1, n2: Optional, generally means “select the number of lines to perform the action”, for example, iffunctionIs required between 10 and 20 lines, is10, 20 (function)
• If you need a regular expression to match a string, use it/{pattern}/matching

Test. TXT content111
222
333
444----- delete non - first2The first3All lines between rows ---------- server11:~# sed -i '2, 3! d' test.txt 
server11:~ # cat test.txt
222
333------ regular expression matches ------------ server11:~# echo 'clswcl.txt' | sed -nr '/.*/p'
clswcl.txt  // /{pattern}/ = /.*/
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Function has the following options

• Function: -a, insert a new line after the line

sed -i '/ specific string /a newline string ' fileName
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• Function: -i, insert a new line before the line

sed -i '/ specific string/I newline string ' fileName
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• Function: -c, modify the specified content line

sed -i '/ specific string /c CSC LWL ' fileName 
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• Function: -d, delete the specified string

sed -i '/ specific string /d' fileName 
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Sed s subcommand: s/{pattern}/{replacement}/{flags}

• If {pattern} contains regular expressions, add -r
• If {pattern} has groupings, the “\n” in {replacement} represents the NTH group and the “&” represents the entire matching string. See examples for details
• The flags parameters are as follows

• The sample

server11:~ # echo -e 'hello 1112 world' | sed -r 's/([a-z]+)( [0-9]+ )([a-z]+)/&/'  
hello 1112 world
server11:~ # echo -e 'hello 1112 world' | sed -r 's/([a-z]+)( [0-9]+ )([a-z]+)/\3\2\1/' 
world 1112 hello
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Refer to the article

• Sed -i command description and introduction