By default, the run-time configuration behaves as specified by the POSIX.1 standard. There is no need to set the environment to access POSIX.1 behavior.
The operating system conforms to IEEE Std 1003.1-1990, Portable Operating System Interface (POSIX) Part 1: System Application Program Interface (API) as amended by IEEE Std 1003.1b-1993, Amendment 1: Realtime Extension (C Language) and IEEE Std 1003.1c-1995, Amendment 2: Threads (C Language).
The operating system meets the requirements of Section 8 of POSIX.1 by reference to ISO/IEC 9899: 1990, Information Technology-Programming Languages-C / ANSI X3.159-1989, Programming Language C.