Non-interactive editor that processes content one line at a time. (Streaming text editor)
parameter
① -f specifies a rule file. When the requirements are complex, there are many contents that need to be matched.
② -n prevents input line output
③ -r expands the regular rule, and the things that cannot be matched can now be matched.
④ -i The modified data will replace the original file
model
①s replacement
② g whole line (can also be a number, replace the number)
③ d delete
④ p print
⑤ a append
⑥ i insert
1. Replacement
cp /etc/passwd /opt
Replace root with ROOT: #The first two slashes are the content to be matched. You can use regular expressions. The middle of the next two slashes is the content to be replaced, which is plain text.
sed 's/root/ROOT/' /opt/passwd
sed 's/root/ROOT/ ; s/mail/MAIL/' /opt/passwd
Use script file:
vim state
script:
s/root/Root/ s/lp/LP/ s/mail/Mail/
Use script file:
sed -f state /opt/passwd
Save the output:
sed -f state /opt/passwd > newfile
Prevent input lines from being displayed automatically:
sed -n 's/root/ROOT/p' /opt/passwd
2. Delete
rm -rf /opt/*
cp /etc/passwd /opt
Delete the first line of the file
sed '1d' /opt/passwd
Delete lines 1 to 2 of the file
sed '1,2d' /opt/passwd
Delete row 2 to last row
sed '2,$d' /opt/passwd
Matches root, delete this line
sed '/root/d' /opt/passwd
Match the root line to a certain line
sed '/root/,2d' /opt/passwd
Delete odd rows
sed '1~2d' /opt/passwd
Delete even rows
sed '0~2d' /opt/passwd
sed can use instructions to delete empty lines in files
sed '/^$/d' /opt/passwd
Remove comments and empty lines from the sshd configuration file
sed '/^#.*/d;/^$/d' /opt/passwd
3. Replacement
rm -rf /opt/*
cp /etc/passwd /opt
The option -i will cause sed to replace the original file with the modified data
sed -i 's/bin/BIN/' /opt/passwd
The g flag enables sed to perform global substitutions
sed 's/root/admin/g' /opt/passwd
Ignore case substitutions
sed 's/Root/admin/gi' /opt/passwd
The g mark allows sed to match characters after the Nth time to be replaced.
echo "thisthisthisthis" | sed 's/this/THIS/2g'
The delimiter in sed can be replaced with other characters, because the s flag will consider the following character as a delimiter
sed 's:adm:text:' /opt/passwd
sed 's|adm|text|' /opt/passwd
Since it is more dangerous when using the -i parameter, when we use the i parameter and add .bak at the end, a backup file will be generated.
sed -i.bak 's/root/admin/' /opt/passwd
If sed is used in a script, it is inevitable to call variables, so the following method can be used to call variables, that is, ‘ ‘ is replaced by ” “
text=hello
echo "hello world" | sed "s/$text/HELLO/"
Replace the contents on the left and right sides of the equal sign
sed "s/\(.*\) = \(.*\)/\2 = \1/" /opt/passwd
4. Append and insert
rm -rf /opt/*
cp /etc/passwd /opt
Insert content in the next line matching the line starting with bin
sed '/^bin/a\hello nihao/' /opt/passwd
Insert content one line above the line that matches the line starting with bin
sed '/^bin/i\hello nihao/' /opt/passwd
