sed -f: Process Text with a Script File

Overview

sed is a powerful tool for editing text streams. Using the -f option, you can save sed commands in a separate script file and execute them. This is very useful for managing complex scripts or when you need to apply multiple sed commands at once.

Key Features

Easy management of complex scripts
Increased script reusability
Consolidation of multiple sed commands into one file
Facilitates version control and sharing

Key Options

These are the commonly used options when using sed -f.

Specifying the Script File

Other Useful Options

Generated command:

Try combining the commands.

Description:

`sed` Executes the command.

Combine the above options to virtually execute commands with AI.

Usage Examples

Various usage examples of the sed -f command.

Using a Basic Script File

echo 'This is an apple.' > input.txt
echo 's/apple/orange/g' > script.sed
sed -f script.sed input.txt

Write the command 's/apple/orange/g' in script.sed and apply it to input.txt.

Script File with Multiple Commands

echo -e 'This is an error.\n# This is a comment.\nAnother error.' > data.txt
echo -e 's/error/ERROR/g\n/^#/d' > multi.sed
sed -f multi.sed data.txt

Write multiple sed commands in multi.sed and apply them to data.txt. (e.g., replace 'error' with 'ERROR', and delete lines starting with '#')

In-Place File Editing with Backup

echo 'This is old_text.' > file.txt
echo 's/old_text/new_text/g' > replace.sed
sed -i.bak -f replace.sed file.txt
cat file.txt
cat file.txt.bak

Modify file.txt directly using commands from replace.sed and create a backup file with the .bak extension.

Printing Specific Lines with the -n Option

echo -e 'Line 1\nLine 2\nLine 3' > log.txt
echo '2p' > print_line.sed
sed -n -f print_line.sed log.txt

Write the command '2p' in print_line.sed to print only the second line of log.txt.

Tips & Precautions

Useful tips and points to note when using sed -f.

Script File Permissions

Script files executed with sed -f do not require execute permissions; only read permissions are necessary.

Debugging

If your sed script is not working as expected, you can use the -n option with the p command to check if specific patterns are matching, or use the l (list) command to view non-printable characters.

Combining -e and -f

You can specify simple commands directly using the -e option and use complex script files with the -f option. This allows for flexible script writing.

Backup File Management

It is safer to create backup files when using the -i option. It is advisable to periodically clean up unnecessary backup files.