Overview

sed edits streams using scripted commands, most often for substitutions.

Syntax

sed [options] 'script' file...

Arguments

• script: Editing instructions.
• file: Optional input files.

Options Table

Examples

sed 's/error/warn/g' app.log
sed -n '10,20p' /etc/ssh/sshd_config

Real-world Usage

Use sed to normalize log output before ingestion or to patch config files during automation.

Common Mistakes

• Using -i without backups.
• Forgetting to escape regex characters.

Performance Notes

sed is efficient for line-level edits. Prefer it over heavier scripting when possible.

Security Considerations

Avoid editing critical configs in place without version control or backups.

Related Commands

awk, grep, perl

Practice Exercises

1. Replace all instances of DEBUG with INFO in a file.
2. Print lines 50 to 80 of a configuration file.