Sed Command and Its Different Usages

sed (Stream Editor) is a powerful command-line tool used for text processing, including search, replace, insert, and delete operations.

Basic Syntax

sed [OPTIONS] 's/SEARCH_PATTERN/REPLACEMENT/FLAGS' FILE

Common Flags

• -i → Edit files in-place (modify original file)
• g → Replace all occurrences in a line (default: only first occurrence)
• p → Print modified lines
• d → Delete lines
• -n → Suppress automatic printing

Usage Examples

1. Replace Text in a File

Replace first occurrence of 'foo' with 'bar' in a file

sed 's/foo/bar/' file.txt

Replace all occurrences of 'foo' with 'bar' in a file

sed 's/foo/bar/g' file.txt

Replace and save changes to the same file

sed -i 's/foo/bar/g' file.txt

2. Replace Text in Multiple Files

sed -i 's/foo/bar/g' *.txt

3. Delete Lines

Delete lines containing 'error'

sed '/error/d' file.txt

Delete empty lines

sed '/^$/d' file.txt

4. Extract Specific Lines

Print lines 5 to 10

sed -n '5,10p' file.txt

5. Update Dates in a File

Update all occurrences of 2021.MM.DD to the current date in a CSV file

sed -i "s/2021\.[0-9]\{2\}\.[0-9]\{2\}/$(date +%Y.%m.%d)/g" file.csv

Update dates in all CSV files in a directory

sed -i "s/2021\.[0-9]\{2\}\.[0-9]\{2\}/$(date +%Y.%m.%d)/g" *.csv

Conclusion

sed is a versatile tool that simplifies text manipulation in Linux. It is widely used for scripting and automation in text processing tasks.

💡 Tip: Always test sed commands without -i before modifying files permanently!

Written by A.M. Rinas