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POSIX is an acronym for Portable Operating System Interface, a family of standards specified by the IEEE for maintaining compatibility between operating systems.

POSIX is a family of standards that specify the behavior of Unix-like operating systems.

These standards define:

  • A standard operating system interface and environment.
  • A programming API for the C programming language.
  • The behavior of a command interpreter (or shell).
  • The behavior of common utility programs invocable from the shell.

The POSIX standards are developed by the Austin Group, sponsored by the Portable Application Standards Committee of the IEEE.

The current set of POSIX standards is available online.