POSIXlike

POSIXlike refers to software, libraries, or operating environments that implement a substantial portion of the POSIX application programming interfaces and behavior, without necessarily asserting full formal POSIX certification. POSIX, short for Portable Operating System Interface, is a family of standards published by IEEE that defines interfaces for compatibility between Unix-like systems. A POSIXlike system aims to offer a familiar API surface for tasks such as file I/O, process management, signals, threading (POSIX threads), and basic shell utilities.

The term is often used in documentation to indicate portability across POSIX-compatible platforms, while acknowledging possible gaps, extensions, or deviations. Real-world POSIXlike implementations may cover POSIX.1 and parts of POSIX.2, with varying levels of conformance and with additional non-POSIX features provided by compilers or C libraries. Differences may include behavior of certain system calls, threading schedulers, time management, or feature tests.

Examples of POSIXlike environments include most modern Unix-like systems, such as Linux, FreeBSD, OpenBSD, and macOS, which expose POSIX-like interfaces. Mobile platforms with POSIX-like layers or libraries (for example, Android with the Bionic C library) provide substantial POSIX compatibility. Windows environments historically offered POSIX-like layers through compatibility projects or subsystems but are not inherently POSIX-compliant.

POSIXlike thus serves as a practical label for software intended to run across diverse platforms with POSIX-inspired interfaces, signaling a balance between broad compatibility and the realities of partial conformance, platform extensions, or implementation-defined behavior. See also POSIX, POSIX compliance, POSIX threads.