Different Types of Files in Linux

A file type helps us identify the type of content saved in the file. Linux supports seven different file types. These are regular, directory, link, character, block, socket, and named pipe.

Regular or ordinary files

Regular or ordinary files store data for various content types such as text, audio, video, images, scripts, and programs. There are hundreds of content types. We can create a regular file with or without an extension.

An extension is a group of characters used with the file name to give it a unique identity or to group it with similar content-type files. Files often use well-known extensions for easy recognition and processing. Although the Linux file system does not need extensions, you should use them. They help us identify the content types saved in files. For example, a file with a .mp4 extension is a video file.

To view a list of all supported content types and file extensions, check the /etc/mime.types file. The MIME (Multipurpose Internet Mail Extensions) provides a standard designation and classification for file content types.

$cat /etc/mime.types

Linux is a multi-user system. It provides a dedicated directory to every user in the /home directory. A user saves his regular files in his home directory.

Directory files

Linux file system uses directories to organize files in a hierarchy. Directories are also files, but instead of storing data, they store the location of other files. A directory uses directory entries to store the files' location in it. Each directory entry stores the name and location of a single file.

Linux file system starts with a directory called / or root directory. It places all files and directories under this directory. Apart from the root directory, every directory has a parent directory.

Special files

Linux treats all hardware devices (such as hard drives, printers, monitors, terminal emulators, and CD/DVD drives) as special files. Applications access and use device files as regular files. This feature makes software development in Linux straightforward and flexible. Linux places all device files under the /dev directory. There are two types of device files: character and block. A character file represents a device that transfers data in bytes, such as a monitor or a printer. A block file represents a device that transfers data in blocks, such as a hard drive.

Link files

Link files allow us to use a file with a different filename or location. A link file is a pointer to another file. There are two types of links: hard and soft or symbolic. A hard link creates a mirror copy of the original file. We can not make a hard link to a directory or a file on another filesystem. However, we can create a soft link to a directory or a file on another filesystem. A soft or symbolic link creates a pointer to the original file.

Socket files

A socket is a communication endpoint that applications use to exchange data. For example, if an application wants to communicate with another application, it connects with the socket of that application. Each application that provides services to other applications or remote clients uses a socket to accept connections. Each socket accepts client connections with an IP address and a unique port number. For example, suppose a local system application wants to communicate with another remote system application. It connects to that application's socket using its IP address and port number.

Sockets are complex. Linux uses socket files to make the communication process more manageable. Socket files allow applications on the local system to exchange data without going through the complex process of networking and sockets. Socket files are special files that use a file name as their address instead of an IP address and port number. Socket files use the sendmsg() and recvmsg() system calls to enable inter-process communication between local applications.

Named pipe files

Linux allows us to send the output of a process or command to another as the input. This feature is known as the pipe. There are two types of pipes: standard and named. A standard pipe only connects processes under the same user account or the parent process. A named pipe connects processes running under different user accounts or parent processes. Named pipe files are the empty pipe files. The kernel processes them without writing to the file system. It uses the FIFO (First In, First Out) mechanism to process them. They can exist anywhere in the file system.

Identifying file types

There are many ways to identify a file's type. The easiest way is to use the file command. It accepts the file name as an argument. For example, the following command displays the file type of the abc file.

$file abc

The output of this command displays the file type of the specified file and the contents stored in it.

You can also use the ls -l command to identify the file type.

$ls -l

In the output, the first character of each entry tells the file type.

Conclusion

Identifying file types is essential while working with the Linux file system. This tutorial explained the file types and commands you need to identify them.