Pseudo file system

In computer science, a synthetic file system or a pseudo file system is a hierarchical interface to non-file objects that appear as if they were regular files in the tree of a disk-based or long-term-storage file system. These non-file objects may be accessed with the same system calls or utility programs as regular files and directories. The common term for both regular files and the non-file objects is node.

The benefit of synthetic file systems is that well known file system semantics can be reused for a universal and easily implementable approach to interprocess communication. Clients can use such a file system to perform simple file operations on its nodes, and do not have to implement complex message encoding and passing methods and other aspects of protocol engineering. For most operations, common file utilities can be used, so even scripting is quite easy.

This is commonly known as everything is a file and is generally regarded to have originated from Unix.

In the Unix-world, there is commonly a special filesystem mounted at /proc. This filesystem is implemented within the kernel and publishes information about processes. For each process, there is a directory (named by the process ID), containing detailed information about the process: status, open files, memory maps, mounts, etc.

/proc first appeared in Unix 8th Edition, and its functionality was greatly expanded in Plan 9 from Bell Labs.

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