sed substitution in Linux CLI - Mini Project: Build & Apply

Basic Text Replacement Using sed Substitution

📖 Scenario: You have a text file that contains a list of fruits. You want to replace one fruit name with another using a simple command.

🎯 Goal: Learn how to use the sed command to substitute text in a file and display the changed content.

📋 What You'll Learn

Create a text file named fruits.txt with specific fruit names.

Define the fruit name to replace using a variable.

Use sed substitution to replace the fruit name in the file content.

Display the updated content on the screen.

💡 Why This Matters

🌍 Real World

Text substitution is common when updating configuration files, logs, or data files automatically without opening them manually.

💼 Career

Knowing how to use sed substitution helps in system administration, automation scripts, and data processing tasks.

1

Create the text file with fruit names

Create a file named fruits.txt with these exact lines:
apple
banana
cherry

Linux CLI

# Create the file fruits.txt with the fruit names
# Your code here

Need a hint?

Use echo with -e and redirect output to fruits.txt.

2

Set the fruit name to replace

Create a variable called old_fruit and set it to banana.

Linux CLI

echo -e "apple\nbanana\ncherry" > fruits.txt
# Set old_fruit variable to banana
# Your code here

Need a hint?

Use old_fruit=banana to assign the variable.

3

Use sed to substitute the fruit name

Use sed with substitution to replace $old_fruit with orange in fruits.txt and save the result to a variable called new_content.

Linux CLI

echo -e "apple\nbanana\ncherry" > fruits.txt
old_fruit=banana
# Use sed substitution to replace $old_fruit with orange and save to new_content
# Your code here

Need a hint?

Use sed "s/$old_fruit/orange/g" fruits.txt and command substitution $( ).

4

Display the updated content

Print the variable new_content to show the updated fruit list with banana replaced by orange.

Linux CLI

echo -e "apple\nbanana\ncherry" > fruits.txt
old_fruit=banana
new_content=$(sed "s/$old_fruit/orange/g" fruits.txt)
# Print new_content
# Your code here

Need a hint?

Use echo "$new_content" to print the updated text.