How to use sed to find and replace text in a file?
Jun 13, 2025 am 12:33 AM
To find and replace text in a file using sed, it can be implemented through the basic command s/old-text/new-text/. 1. Replace the first match per line by default, such as sed 's/Hello/Hi/' example.txt; 2. Add g parameter to replace all matches, such as sed 's/Hello/Hi/g' example.txt; 3. Replace specific lines by line number, such as sed '3s/old/new/' example.txt; 4. Replace multiple lines with ranges, such as sed '2,5s/old/new/' example.txt; 5. Replace rows that meet the conditions in combination with regular expressions, such as sed '/error/s/old/new/' example.txt; 6. Use the -i parameter to modify the file directly, but be careful; 7. Use other symbols to delimit special characters, such as sed 's#/usr/local/bin#/opt/bin#' example.txt; 8. When replacing content with variables, wrap the expression in double quotes, such as sed "s/$old/$new/" fruit.txt.
Of course, here is an article on how to find and replace text in a file using sed :
It is not actually complicated to use sed to find and replace text in a file. Its basic usage is to complete the replacement operation through expressions such as s/old-text/new-text/ . For example, if you have a text file, there is a line of content that says Hello world . If you want to change it to Hello there , you can use sed to implement it quickly.
Replace the first match in the file
By default, sed will only replace the first matching string in each line.
The command format is as follows:
sed 's/old content/new content/' file name
For example, if you run:
sed 's/Hello/Hi/' example.txt
It will only replace the first Hello in each line to Hi , the output will not change the original file, it will only be printed on the terminal. If you want to save the result back to the file, you can add a redirect:
sed 's/Hello/Hi/' example.txt > temp.txt && mv temp.txt example.txt
Or directly modify the original file in a system that supports -i parameters (such as Linux):
sed -i 's/Hello/Hi/' example.txt
Replace all matches in a row
If you want to replace all the strings that appear in a certain line, instead of just replacing the first one, you can add g (the meaning of global):
sed 's/Hello/Hi/g' example.txt
This will replace all Hello in each row with Hi .
Replace content of a specific line
Sometimes we just want to replace a specific line, not the entire file. At this time, you can use line numbers to limit the range. For example:
sed '3s/old/new/' example.txt
This command will only replace the first old on line 3 to new .
If you want to replace a line in a range, such as lines 2 to 5, you can write it like this:
sed '2,5s/old/new/' example.txt
You can also combine regular expressions, such as replacing only the line containing a certain keyword:
sed '/error/s/old/new/' example.txt
This command will be replaced in the line containing error .
Notes and some small details
Be careful when using the
-iparameter, because it will directly modify the original file , and it is recommended to back up first.If you want to replace the content with special characters (such as
/), you can use other symbols instead of the delimiter, such as#or|:sed 's#/usr/local/bin#/opt/bin#' example.txt
If there are variables in the replacement content, remember to wrap the expression in double quotes to facilitate inserting shell variables:
old="apple" new="orange" sed "s/$old/$new/" fruit.txt
Basically that's it. By mastering these common methods, you can meet the text replacement needs in most scenarios.
The above is the detailed content of How to use sed to find and replace text in a file?. For more information, please follow other related articles on the PHP Chinese website!
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