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sed Examples Cheat Sheet

Edit streams and files with sed substitutions, filters, and in-place updates for fast text transformations.

What this cheat sheet is for

This sed examples reference helps you complete common developer tasks quickly and avoid repeated trial-and-error when working under deadlines.

  • When you need a reliable command or pattern during debugging and incident response.
  • When you are implementing a feature and want a known-good syntax example immediately.
  • When onboarding teammates and documenting repeatable workflows for daily use.
  • When reviewing pull requests and verifying that command usage follows best practices.
  • Replace config values across files.
  • Delete matching log lines before sharing.
  • Extract specific line ranges from output.

Substitution patterns

Replace first match per line

sed "s/foo/bar/" input.txt

Example:

sed "s/localhost/127.0.0.1/g" .env

Use regex capture groups

sed -E "s/(v)([0-9]+)/\1-\2/" tags.txt

Example:

sed -E "s#https?://##" urls.txt

In-place editing

Edit file in place (GNU sed)

sed -i "s/debug=false/debug=true/" app.conf

Example:

sed -i.bak "s/8080/9090/" app.conf

Delete lines matching pattern

sed -i "/^#/d" .env

Example:

sed "/ERROR/d" app.log

Line selection and printing

Print line ranges

sed -n "1,20p" server.log

Example:

sed -n "/BEGIN/,/END/p" output.txt

Print matching lines only

sed -n "/timeout/p" app.log

Example:

sed -n "5p" file.txt

Common mistakes / Pitfalls

  • macOS and GNU sed differ for -i syntax; test before scripting.
  • Unescaped slashes in replacement text can break substitution commands.
  • In-place edits without backup can permanently damage important files.

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Last updated: February 2026