How to Use the sed Command in Linux

Stands for “Stream Editor”. “sed” is a utility command that take file content or standard input (stdin) and modify the output through RegEx pattern. It’s generally a handy command to use to modify content within a file.

General syntax for sed command:

$ sed [OPTIONS] [FILE]...
Text substitution
echo "Text" | sed 's/Replaceable_Word/The_Word_That_Replaces/'

Use the sed command to search and replace any part of the text. 's' indicates a search and replace task.

Example: Finding the word “CSS” in the text “CSS Libraries” and replacing it with the word “JavaScript.”

text substitution
Replace text on a specific line in a file
sed '[line] s/harder/easier/g' [file]

The 'g' option of the sed command is used to replace anything that matches the pattern.

Example: Let’s replace the word “harder” in the first line of the libraries.txt file. Note: “harder” occurs twice in the line.

replace text in file
Replace first matching with new text
sed 's/harder/easier/' [file]

This command replaces only the first match of the search pattern.

Example: Replacing the first occurrence of the word “CSS” in the example.txt file with the word “JavaScript”

replace first match
Remove matching lines
sed '/Something/d' example.txt

Use the d option of the sed command to remove any line from a file.

Example: Deleting those lines in the example.txt file that contain the text “Something”

remove matchingkline
Search for a case-insensitive word + delete it
sed '/Sample/Id' example.txt

The I option of the sed command is used to search for a matching pattern in a case insensitive way.

Example: Finding a line containing the word ‘Sample’ and seeing the line delete with and without option in the example.txt file.

search and delete
Replace words with uppercase
sed 's/\(libraries\)/\U\1/Ig' example.txt

Use the U option of the sed command to convert any text to uppercase letters.

Example: Searching for the word “libraries” in the example.txt file and replacing it with uppercase letters.

replace with uppercase
Replace words with lowercase
sed 's/\(libraries\)/\L\1/Ig' example.txt

The L option of the sed command is used to convert any text to lowercase letters.

Example: Searching for the word “libraries” in the example.txt file and replacing it with lowercase letters.

replace with lowercase
Insert blank lines in a file
sed G [file]

Use the G option of the sed command to insert blank lines after each line of the file.

Example: Displaying the file before using the option. Then we use the command and see that after each line, empty lines appeared.

insert blank lines in file
Print file’s line numbers
sed '=' [file]

The = sign is used to print a line number before each line of text in a file.

Example: Following the use of the command, the line numbers appear after each line in the example.txt file.

print files number of lines
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