3 File – What is .3 file and how to open it?

File Format and Usage:

A .3 file extension is associated with the Unix Section 3 Manual Pages. These manual pages provide detailed documentation for Unix commands, system calls, library functions, and other system-related topics. The content of .3 files is written in a special markup language called mdoc (Manual Document), which is processed by the nroff or groff text formatting tools to generate formatted output. The resulting output can be displayed on the terminal or saved as a PDF or HTML document for offline reference.

History and Availability:

The .3 file extension has been part of the Unix operating system since its early days and is still widely used today. It is primarily utilized by system administrators, programmers, and experienced users who need in-depth information about system components and commands. The manual pages are organized into sections, with the .3 extension representing the third section, which is dedicated to library functions. To access the manual pages, users can use the ‘man’ command followed by the name of the topic they want to learn about. For example, to view the manual page for the ‘printf’ function, one would type ‘man 3 printf’ on the command line.

Opening .3 Files on Different Operating Systems

.3 files, also known as Unix Section 3 Manual Pages, provide detailed documentation on various commands, functions, and system calls in Unix-like operating systems. To open these files, the specific approach depends on the operating system being used.

On macOS and Linux systems, .3 files can be viewed using the man command. This command opens a terminal window and displays the contents of the specified manual page. For example, to open the manual page for the ls command, type the following command:


man ls


On Windows systems, .3 files can be opened using a text editor such as Notepad++. Alternatively, third-party software dedicated to viewing man pages can be used. One such program is Manic, which provides a graphical interface for navigating and searching through manual pages.

Third-Party Applications for Opening .3 Files

In addition to using the native command line tools or text editors, several third-party applications are available for opening and managing .3 files. These applications often provide additional features such as keyword searching, bookmarking, and hyperlinking to related documentation.

Some popular third-party applications for opening .3 files include:

• ManViewer (macOS)
• Manim (Linux)
• XMan (Windows)
• 3View (cross-platform)

These applications offer user-friendly interfaces and advanced features that enhance the experience of working with Unix Section 3 Manual Pages. By leveraging these tools, users can efficiently access the extensive documentation available on various Unix commands and functions.

File Extension .3

The “.3” file extension is associated with Unix Section 3 Manual Pages, a type of documentation format used in Unix-like operating systems. Manual pages provide detailed information about commands, system calls, functions, and other aspects of the system. They are typically organized into three sections:

• Section 1: User Commands
• Section 2: System Calls
• Section 3: C Library Functions

File extensions are used to identify the type of data contained within a file. Files with the “.3” extension specifically indicate that they contain manual page information for Unix-like operating systems. These files are typically formatted in ASCII text and can be viewed using a text editor or a dedicated manual page viewer.

History and Development

Manual pages have been a fundamental part of Unix systems since their inception in the 1970s. The original manual pages were written by Dennis Ritchie and Ken Thompson, the creators of the Unix operating system. Over time, manual pages have evolved to become a comprehensive and widely used resource for Unix users.

The “.3” file extension is specifically associated with Section 3 manual pages, which document the functions provided by the C standard library. These functions are essential for developing C programs and are widely used in various software applications. By providing detailed information about function prototypes, parameters, return values, and usage examples, manual pages greatly facilitate the development and understanding of software code.

Other Extensions