The less command in Linux is used for viewing file contents in a paginated way, which is particularly helpful for large files that don't fit on a single screen. Unlike cat, less lets you scroll up and down through a file, search for text, and view portions of the content without loading the entire file into memory.

Basic Syntax

less [options] file

Key Features of less

• Scrolling: View content page-by-page or line-by-line.
• Searching: Find specific text patterns within the file.
• Navigation: Move through the file using keyboard commands.

Example with Output

Example 1: Viewing a File

Using less to view a file opens it in a paginated format, allowing you to scroll through the content.

Command

less file.txt

Output (on-screen navigation)

This is the content of file.txt.
It spans multiple lines and pages.
----
(END)

Explanation:

• When you open file.txt with less, only a portion of the file appears on the screen.
• You can scroll down with Enter (line-by-line), Space (page-by-page), or scroll up with b.
• Press q to quit and return to the command prompt.

Example 2: Searching for Text in a File

Within less, you can search for specific text patterns using / followed by the search term.

Command

less file.txt

Then, within less, type:

/word

Output

This is the content of file.txt.
Here is the searched word in the middle of the content.
----

Explanation:

• /word searches for the first instance of "word" in file.txt.
• Press n to move to the next occurrence and N to move to the previous one.

Example 3: Displaying Line Numbers

The -N option displays line numbers in the less viewer, making it easier to reference specific lines in the file.

Command

less -N file.txt

Output

1 This is the content of file.txt.
2 Here is some additional text.
3 This is the last line.
----
(END)

Explanation:

• less -N file.txt shows line numbers on the left side of each line.
• Line numbers help identify specific sections, especially in large files.

Example 4: Viewing Output from Another Command

You can pipe the output of other commands (e.g., ls -l) to less to view long command output more easily.

Command

ls -l | less

Output

total 16
-rw-r--r-- 1 user user 1234 Oct 29 10:00 file1.txt
-rw-r--r-- 1 user user 5678 Oct 29 10:10 file2.txt
----
(END)

Explanation:

• ls -l | less shows the output of the ls -l command one page at a time.
• This is useful for commands with long output, so you don’t miss any details.

Navigation Commands Within less

Once in less, you can use various keyboard commands for navigation:

Summary of Common less Commands

• less file.txt: View the file with scrolling capabilities.
• less -N file.txt: View the file with line numbers.
• ls -l | less: View the output of ls -l with pagination.
• Within less, use /search_term: Search for text patterns in the file.

The less command is an efficient, user-friendly way to navigate large files in Linux, providing fast scrolling, text searching, and various navigational tools without modifying the file content.