POSIX

POSIX is a family of IEEE standards for portable interfaces between applications and operating systems, covering system APIs, command-line utilities, and shell behavior.

IEEE 1003.1: The IEEE standard that specifies core POSIX system interfaces, shell, and utilities. It is the central standard in the POSIX family and contains most commonly cited requirements.
POSIX API: The standardized functions and data types applications use to interact with POSIX-conforming operating systems. These interfaces let programs use common services without depending on vendor-specific APIs.
POSIX compliance: Conformance of an operating system or program to specified POSIX requirements. Compliance determines which standardized interfaces applications can safely assume are available.
Windows API: The native set of programming interfaces used by applications on Microsoft Windows. It is a major alternative to POSIX interfaces for operating-system services.
POSIX.1: The core POSIX standard for operating-system interfaces, shell, and utilities. This name commonly identifies the standard's main interface specification.
POSIX shell: The command-language interface specified by POSIX for interpreting scripts and interactive commands. Its defined syntax and behavior make shell scripts more portable across compliant systems.
Portable operating system interface: A standardized boundary through which software accesses operating-system services. POSIX is a prominent family of specifications for this broader kind of interface.
Linux system call interface: The low-level interface through which Linux user programs request kernel services. Linux system calls are not identical to the standardized POSIX API exposed by libraries.
POSIX.2: A historical POSIX standard specifying shell and utility behavior. It separated command-language and utility requirements before these were integrated into IEEE 1003.1.
POSIX utilities: Command-line programs whose names, options, and behavior are specified by POSIX. Their shared contracts make common command sequences less dependent on a particular Unix distribution.

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