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LPI Linux Essentials Exam 010-160 - Topic 3.2 - less Pager

The less command in Linux is designed to provide a user-friendly interface for viewing text files one screen at a time. It facilitates both forward and backward navigation through the file, setting it apart from other pager programs. Notably, less does not require loading the entire file before displaying it, which is especially beneficial for large files.

Usage

To view a file using the less command, simply type less followed by the file’s name:

less filename

Alternatively, you can pipe data to less for paging through which is useful when extracting and manipulating data:

command | less

Common Navigation Commands

The table below summarizes some of the common navigation commands available in less:

Command Description
SPACE Scroll forward one screen
b Scroll backward one screen
d Scroll forward half a screen
u Scroll backward half a screen
G Go to the end of the file
g Go to the beginning of the file
/pattern Search forward for a pattern
?pattern Search backward for a pattern
n Repeat the previous search
N Repeat the previous search in the opposite direction
q Quit less

Common Use Cases

Viewing Large Log Files

less is highly useful for viewing large log files, as it allows you to start viewing the file immediately without waiting for the entire file to load:

less /var/log/syslog

Searching Through Text

less provides powerful search functionality, allowing you to search both forward and backward through a text file. After initiating a search, you can use n and N to navigate through the search results:

less filename
/pattern

Viewing Compressed Files

less can directly view compressed files without the need to decompress them first:

less file.gz

Viewing Multiple Files

less allows you to view multiple files by specifying multiple filenames when you start less. You can then navigate between the files using the :n and :p commands:

less file1 file2
:n
:p

Conclusion

The less command is an essential tool for Linux users, providing a wide range of features for viewing and navigating through text files. Whether you are dealing with large log files, searching through text, or simply reading documentation, less offers a user-friendly and efficient solution. Its ability to display files without loading the entire content, combined with its extensive navigation and search capabilities, makes less a go-to tool for viewing data.