Master the less Command: Your Linux File Browser

What is the less Command?

Envision the Linux filesystem as a library, and the less command as your librarian, letting you page through large files one screen at a time. Type less log.txt to view log.txt interactively, scrolling with arrow keys.

Why less is Essential

Syntax and Options

The less command is interactive:

less [options] file
        

Key options:

• -N: Display line numbers.
• -i: Ignore case in searches.
• -S: Chop long lines (no wrapping).
• -g: Highlight only the last search match.

Key navigation: Space (next page), b (previous page), /pattern (search), q (quit).

Real-World Examples

1. View a File

Type this:

less log.txt
        

Opens log.txt for interactive viewing.

2. Display Line Numbers

View with line numbers:

less -N script.sh
        

Shows line numbers for each line.

3. Case-Insensitive Search

Search ignoring case:

less -i log.txt
        

Then type /error to search for “error” or “ERROR”.

4. View Piped Output

View command output:

ls -l | less
        

Displays ls -l output in less.

5. Scripting with less

View logs in a script:

#!/bin/bash
less +F /var/log/syslog
        

Follows syslog in real-time (like tail -f).

Advanced Usage

Master less with these techniques:

• Jump to Line: Use :n to jump to line n.
• Follow Mode: Use less +F to monitor file changes.
• Multiple Files: Use less file1.txt file2.txt and :n/:p to switch.
• Search Navigation: Use n (next match) and N (previous match).

Example: Monitor a log file:

less +F /var/log/app.log
        

Pro Tips

Efficient Scrolling: Use Ctrl+F to jump forward multiple lines.

Search Highlighting: Use -g to highlight only the last match.

Alias Shortcut: Set alias l='less -N' for line-numbered viewing.

Common Mistakes to Avoid

Avoid these pitfalls with less:

• Forgetting to Quit: Press q to exit; don’t leave less running.
• Binary Files: Avoid less for binary files; use strings or hexdump.
• Overusing cat: Use less instead of cat for large files.

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