.5 File Extension
What is a 5 file?
A 5 file contains a Unix system-level manual page (man page) that likely documents a file format or convention. It is named for the format or convention it documents. You can access 5 files using the man utility.
Unix-like OSes include a system manual that is divided into eight numbered sections. This manual's fifth section usually describes the file formats the system supports. Each supported format is documented in a separate 5 file.
For example, the file deb.5 describes the .DEB file format. It also provides a list of additional related entries.
In some Unix systems, such as System V, 5 files instead contain documentation of miscellaneous system information. These 5 files can still be accessed using the man utility.
How to open a 5 file
In Unix-like OSes, you can open a 5 file by calling the man utility using the name of the file. For example, to open deb.5, enter man deb(5).