POSIX standards and features

Portable Operating System Interface (POSIX) for Unix represents a series of standards for operating system interfaces. The first version dates back to 1988 and covers a series of topics like filenames, shells, and regular expressions.

There are many features defined by POSIX, and they are organized in four different standards, each one focusing on a different aspect of the Unix compliance. They are all named POSIX followed by a number.