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What is POSIX?
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- hwahyeon
Portable Operating System Interface + X, abbreviated as POSIX, is an Application Programming Interface (API) standard established by IEEE to ensure compatibility and portability across Unix and Unix-like operating systems. POSIX enables applications to function consistently in different Unix environments, with non-Unix OSes, such as Microsoft Windows, excluded from its scope. Operating systems that adhere to POSIX standards are considered Unix-like.
Linux, although not officially POSIX-certified, supports most POSIX APIs through the GNU C Library (glibc) and is thus classified as a Unix-like OS. Unix-like OSes can be grouped by their level of POSIX compliance as follows:
- Fully certified: Operating systems like macOS that have obtained POSIX certification.
- Mostly compliant but uncertified: Operating systems like Linux that largely follow POSIX standards without formal certification.
- Partially compatible: Operating systems that implement only specific POSIX features to improve compatibility.
POSIX has become a widely applicable standard beyond Unix systems, serving as a key measure of portability and compatibility that allows applications to function across various platforms without dependency on a specific OS.