Chapter 4: Viewing and Editing Files in WSL Ubuntu (cat, nano, vim, less)

In Linux, working with files often means using the terminal. Whether you’re reading logs, editing config files, or writing scripts, you’ll rely on powerful command-line tools.

This chapter covers essential commands for viewing and editing files: cat, less, nano, and vim. Each has its strengths — and once you get comfortable, you’ll never need a GUI for quick edits.

📄 Viewing Files in the Terminal

📌 cat – View Entire File (No Scroll)

Displays the contents of a file directly in the terminal.

cat filename.txt

Good for short files. For longer files, use less.

📌 less – Scroll Through Long Files

Allows you to scroll up and down through long files easily.

less filename.txt

• ↑/↓ or PageUp/PageDown – scroll
• q – quit
• /word – search forward
• n – next result

📌 head & tail – View Top/Bottom of Files

head filename.txt       # First 10 lines
tail filename.txt       # Last 10 lines
tail -f logfile.log     # Live updates (logs)

📝 Editing Files in the Terminal

📌 nano – Simple Text Editor

Beginner-friendly and easy to use. Ideal for quick config changes.

nano myfile.txt

Basic nano controls:

• Ctrl + O – Save
• Ctrl + X – Exit
• Ctrl + K – Cut line
• Ctrl + U – Paste line

📌 vim – Powerful Editor (Advanced Users)

vim is a highly powerful terminal editor but has a learning curve.

vim myfile.txt

Vim basics:

• i – Insert mode (start editing)
• Esc – Command mode
• :w – Save
• :q – Quit
• :wq – Save and quit
• dd – Delete line
• u – Undo

If vim is not installed, you can install it using:

sudo apt install vim

📌 Pro Tips

• Use less to read long log files like /var/log/syslog
• Edit config files like .bashrc using nano ~/.bashrc
• Combine commands: cat filename.txt | grep "searchword"

🧪 Practice Task

Open Ubuntu WSL and try the following:

# Create and edit a file
nano mynotes.txt
# Type some text, save and exit (Ctrl+O, Enter, Ctrl+X)

# View with cat and less
cat mynotes.txt
less mynotes.txt

# Add more lines
echo "New line added" >> mynotes.txt
head mynotes.txt
tail mynotes.txt

# Try vim (optional)
vim mynotes.txt

✅ Summary

• cat – Quick file output
• less – Scrollable viewing
• nano – Beginner-friendly text editor</li