CIS120 Linux Fundamentals by Scott Shaper

The less Command

Think of the less command as a smart way to read files in Linux. It's like having a book reader that lets you scroll through text files easily, search for specific words, and jump to different parts of the file. Unlike regular text editors, less is perfect for quickly viewing files without making changes.

What is Less?

less is a command-line tool that helps you view and navigate through text files. It's called "less" because it's "more" than the older more command (get it?). It's one of the most useful tools you'll use in Linux, especially when working with large files or log files.

Basic Usage

To start using less, just type the command followed by the name of the file you want to view:

less filename.txt

This opens the file in a viewer where you can scroll through it. The file stays in its original state - you're just looking at it, not changing it.

Navigation Keys

Here are the most important keys you'll use to move around in less:

Key What It Does
Up/Down Arrows or j/k Move up or down one line at a time
Page Up/Page Down or [SPACE]/[b] Move up or down one screen at a time
G Jump to the end of the file
1G or gg Jump to the beginning of the file
/pattern Search for text (press n for next match)
?pattern Search backwards (press N for previous match)
q Quit and return to the command line

Practical Examples

Viewing a File

Let's say you have a file called notes.txt with your class notes:

less notes.txt

This opens your notes file for viewing. You can scroll through it using the arrow keys or page up/down.

Finding Information

Need to find something specific in a long file? Use the search feature:

less notes.txt

Then type /homework to find the word "homework" in your notes. Press n to find the next occurrence.

Viewing System Logs

System logs can be very long. less is perfect for viewing them:

less /var/log/syslog

Use G to jump to the end and see the most recent entries.

Useful Options

Here are some helpful options you can use with less:

Option What It Does When to Use It
-N Shows line numbers When you need to reference specific lines
-i Ignores case in searches When you're not sure about capitalization
-S Truncates long lines When viewing files with very long lines
+<number> Starts at line number When you want to jump to a specific part

Tips for Success

Common Mistakes to Avoid