01-09 Linux Three Musketeers-sed

definition

sed is a stream editor that processes one line of content at a time

The process of text processing: ( mode space is the key )

Format: sed [-hn][-e<script>][-f<script file>][file]

• -h : Display the help file\
• -n : Only display the processed results of script
• -e<script> : The script specified in the option has been used to process the input text file\
• -f<script file>: The script file specified in the option has been used to process the input text file\

Common actions (the below 16129df00b6eee will not change the content of the source file )

• a : add new; sed -e '4 a newline' : add a new line after line 4\
• c : Replace; sed -e '2-5 c No 2-5 number' \
• d : delete; sed -e '2,5 d' : delete the second and fifth lines\
• i : insert; sed -e '2 i newline' : insert a row before the second row\
• p : print; sed -n '/root/p' : only print the line containing root; /***/ represents the regular matching syntax script\
• s : replace; sed -e 's#old#new#g' : replace old with new, g represents global replacement; # can be replaced with /，@ etc.\

Practical application

• Add a new string after line 4

$ cat test
root root hello root
root
root
leo
kate
hogwart
string
leon
$ sed -e '4 a newline' test
root root hello root
root
root
leo
newline  # 新插入的行
kate
hogwart
string
leon

• Add a new string before line 2

$ sed -e '2 i newline' test
root root hello root
newline  # 在第2行前添加
root
root
leo
kate
hogwart
string
leon

• Global replacement

$ sed -e 's/root/hello/g' test
hello hello hello hello
hello
hello
leo
kate
hogwart
string
leon

• Modify the source file directly; Note: The source file must be backed up in

$ sed -i 's/root/user/' test
$ cat test
user root hello root
user
user
leo
kate
hogwart
string
leon

Course practical application

• Combine the w command to view the number of online people

w | sed '1, 2d' | awk '{print $1}' | sort | uniq -c | wc -l