Mastering sed: 30+ Powerful Text Manipulation Tricks for Linux

What is sed?

sed (Stream Editor) is a command‑line utility that edits text streams without opening files, allowing you to substitute, delete, insert, or print text directly from the terminal.

Basic Operations

Replace text : sed 's/old/new/' file.txt Global replace (all matches): sed 's/old/new/g' file.txt In‑place edit (modify the file): sed -i 's/old/new/g' file.txt Use -i.bak to keep a backup.

Delete a line by number : sed '2d' file.txt Delete the last line : sed '$d' file.txt Delete lines matching a pattern : sed '/pattern/d' file.txt Print specific lines (e.g., line 2): sed -n '2p' file.txt Print a range of lines (2‑4): sed -n '2,4p' file.txt Insert text before a line : sed '2i\Inserted line' file.txt Append text after a line : sed '3a\Appended line' file.txt Change a specific line :

sed '3c\New content' file.txt

Advanced Patterns

Remove leading and trailing whitespace: sed 's/^[ \t]*//;s/[ \t]*$//' file.txt Strip HTML tags: sed 's/<[^>]*>//g' file.html Delete comment lines starting with # or //:

sed '/^#/d' config.txt
sed '/^\/\//d' code.cpp

Using Multiple Commands

The -e option lets you chain several operations in one call.

sed -e 's/Alice/Jane/' -e 's/Bob/John/' file.txt

You can also combine deletion and substitution:

sed -e '/^#/d' -e 's/error/ERROR/g' file.txt

Combining sed with Other Tools

Batch edit many files with find:

find /path -type f -name "*.txt" -exec sed -i 's/hello/hi/g' {} +

Modify only lines that contain a pattern using grep: grep "error" file.txt | sed 's/failed/FAILED/g' Target a specific column in CSV files with awk and sed:

awk -F, '{ $2=gensub(/low/,"LOW","g",$2); print }' OFS=, file.csv

Process many files efficiently with xargs:

find /var/log -type f -name "*.log" | xargs sed -i 's/DEBUG/INFO/g'

Preview changes before writing using tee:

sed 's/8080/9090/g' config.conf | tee new_config.conf

Show a diff of the transformation before applying it:

diff <(cat file.txt) <(sed 's/error/ERROR/g' file.txt)

Conclusion

sed is a versatile stream editor for searching, replacing, deleting, and inserting text. By mastering its basic commands and learning to combine it with tools like find, grep, awk, xargs, and tee, you can automate repetitive text‑processing tasks, clean logs, update configuration files, and handle structured data efficiently.