sed Command Examples in Linux¶

Introduction¶

These examples show practical ways to use sed on a Linux terminal. Each example is written so you can adapt it for administration or troubleshooting.

Example 1: Basic Usage¶

sed 's/old/new/' file.txt

This is the simplest form of the command and is a good starting point before adding options.

Example 2: Common Admin Task¶

sed -n '1,20p' /etc/ssh/sshd_config

This example reflects a common task on RHEL, Rocky Linux, AlmaLinux, or similar systems.

Example 3: Useful Option¶

sed '/debug/d' app.conf

This option helps narrow the result, change behavior, or handle a more realistic target.

Example 4: Real-World Scenario¶

sed -i.bak 's/enabled=false/enabled=true/' app.conf

Use this pattern when the task moves beyond a single basic command.

Example 5: Verification¶

sed --version

Example output:

https://example.com
https://cloudarks.com

Common Mistakes¶

• Using sed -i without a backup on important files.
• Forgetting the g flag when every match on a line must be replaced.
• Choosing a delimiter that conflicts with paths or URLs and makes the expression hard to read.

Quick Reference¶

sed 's/old/new/' file.txt
sed -n '1,20p' /etc/ssh/sshd_config
sed '/debug/d' app.conf
sed -i.bak 's/enabled=false/enabled=true/' app.conf
sed --version

Related Guides¶

• What is sed?
• sed replace text explained
• sed In-Place Editing
• sed interview questions

Summary¶

Good sed usage means choosing the right option, keeping the target clear, and verifying the result with output you can explain.