IEEE/Open Group 1003.1-2017

IEEE Std 1003.1-201x defines a standard operating system interface and environment, including a command interpreter (or "shell"), and common utility programs to support applications portability at the source code level. It is intended to be used by both applications developers and system implementors. IEEE Std 1003.1-201x comprises four major components (each in an associated volume): 1. General terms, concepts, and interfaces common to all volumes of IEEE Std 1003.1-201x, including utility conventions and C-language header definitions, are included in the Base Definitions volume of IEEE Std 1003.1-201x. 2. Definitions for system service functions and subroutines, language-specific system services for the C programming language, function issues, including portability, error handling, and error recovery, are included in the System Interfaces volume of IEEE Std 1003.1-201x. 3. Definitions for a standard source code-level interface to command interpretation services (a "shell") and common utility programs for application programs are included in the Shell and Utilities volume of IEEE Std 1003.1-201x. 4. Extended rationale that did not fit well into the rest of the document structure, containing historical information concerning the contents of IEEE Std 1003.1-201x and why features were included or discarded by the standard developers, is included in the Rationale (Informative) volume of IEEE Std 1003.1-201x. The following areas are outside of the scope of IEEE Std 1003.1-200x: * Graphics interfaces * Database management system interfaces * Record I/O considerations * Object or binary code portability * System configuration and resource availability IEEE Std 1003.1-200x describes the external characteristics and facilities that are of importance to applications developers, rathere than the internal construction techniques employed to achieve these capabilities. Special emphasis is placed on those functions and facilities that are needed in a wide variety of commercial applications.

Several principles guided the development of POSIX.1-2017: • Application-Oriented - The basic goal was to promote portability of application programs across UNIX system environments by developing a clear, consistent, and unambiguous standard for the interface specification of a portable operating system based on the UNIX system documentation. POSIX.1-2017 codifies the common, existing definition of the UNIX system. • Interface, Not Implementation - POSIX.1-2017 defines an interface, not an implementation. No distinction is made between library functions and system calls; both are referred to as functions. No details of the implementation of any function are given (although historical practice is sometimes indicated in the RATIONALE section). Symbolic names are given for constants (such as signals and error numbers) rather than numbers.

Revision Standard - Superseded. POSIX.1-2017 is simultaneously IEEE Std 1003.1-2017 and The Open Group Standard Base Specifications, Issue 7. POSIX.1-2017 defines a standard operating system interface and environment, including a command interpreter (or "shell"), and common utility programs to support applications portability at the source code level. POSIX.1-2017 is intended to be used by both application developers and system implementors and comprises four major components (each in an associated volume): -General terms, concepts, and interfaces common to all volumes of this standard, including utility conventions and C-language header definitions, are included in the Base Definitions volume. -Definitions for system service functions and subroutines, language-specific system services for the C programming language, function issues, including portability, error handling, and error recovery, are included in the System Interfaces volume. -Definitions for a standard source code-level interface to command interpretation services (a "shell") and common utility programs for application programs are included in the Shell and Utilities volume. -Extended rationale that did not fit well into the rest of the document structure, which contains historical information concerning the contents of POSIX.1-201x and why features were included or discarded by the standard developers, is included in the Rationale (Informative) volume. The following areas are outside the scope of POSIX.1-201x: -Graphics interfaces -Database management system interfaces -Record I/O considerations -Object or binary code portability -System configuration and resource availability POSIX.1-2017 describes the external characteristics and facilities that are of importance to application developers, rather than the internal construction techniques employed to achieve these capabilities. Special emphasis is placed on those functions and facilities that are needed in a wide variety of commercial applications.