POSIX
lastmod 2025-01-09created 2014-02-1613 edits
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The Portable Operating System Interface (POSIX /ˈpɒzɪks/[*]) is an application interface specification defined by the IEEE that organizes the common APIs of different UNIX operating systems, with the aim of developing highly portable Unix applications.
The final letter X in POSIX comes from the X commonly attached to the names of Unix-compatible operating systems.
The specification covers a wide range of areas: not only system calls, the C language interface to the kernel, but also the process environment, files and directories, system databases (the password file, etc.), the tar compression format, and more.
Besides the Unix family, Microsoft Windows NT ships a POSIX subsystem conforming to POSIX 1.0, and POSIX applications can run on that subsystem. This is mainly because the procurement requirements for computer systems of US government agencies (FIPS) require POSIX compliance. The POSIX subsystem shipped up to Windows 2000 but was dropped in Windows XP. Since Windows 2003 R2, POSIX has been supported through the Subsystem for UNIX-based Applications (SUA), which conforms to POSIX 2.0.
POSIX C Library
(Also accessible via POSIX:C Library.) The C POSIX library is a specification of a C standard library for POSIX systems. It was developed at the same time as the ANSI C standard. Some effort was made to make POSIX compatible with standard C; POSIX includes additional functions to those introduced in standard C.