less - Linux

Overview

The less command in Linux is a terminal pager program used to view the contents of a text file one screen at a time. Unlike editors, less does not need to load the entire file before viewing, making it faster and more memory-efficient, especially with large files. It is most effective for quickly viewing or searching through large log files or any long texts.

Syntax

The basic syntax of the less command is:

less [options] file_name
  • file_name is the name of the file you want to view. Multiple files can be specified if needed.

Options/Flags

Here are some commonly used options in less:

  • -N or --LINE-NUMBERS: Displays line numbers in the left margin.
  • -S or --chop-long-lines: Causes long lines to be chopped rather than wrapped.
  • -F or --quit-if-one-screen: Exits if the entire file can be displayed on the first screen.
  • -R or --RAW-CONTROL-CHARS: Displays raw control characters and allows colored text.
  • -i or --ignore-case: Searches are case-insensitive unless search pattern contains upper case letters.
  • -X or --no-init: Does not clear screen after exiting less.

Examples

  1. Viewing a File: Simply open a file with:

    less myfile.txt

  2. View a File with Line Numbers:

    less -N myfile.txt

  3. Searching Inside a File: After opening a file, type /search_term and press Enter to search for search_term in the text.

  4. Exiting less: Press q to quit.

Common Issues

  • File not loading: Ensure the file name is correct and that you have the necessary permissions to read the file.
  • Control Characters Being Displayed: Use -R flag to handle raw control characters if the file contains color encoding or other control sequences.

Integration

less is often combined with other commands for powerful text processing. For example:

  • Combining with grep: Pipe grep output to less for easy reading: 
    grep "error" log.txt | less
  • Viewing Compressed Files: Use zless for compressed files. It is essentially a less command pre-configured to handle gzipped files: 
    zless file.gz
  • more: An older utility with less functionality.
  • grep: For searching through text.
  • tail: For viewing the end of a text file.
  • head: For viewing the start of a text file.

For more information on the less command, the complete manual can be found through the command:

man less

or by visiting the official GNU documentation online.