C POSIX library

The C POSIX library is a specification of a C standard library for POSIX systems. It was developed at the same time as the ANSI C standard. Some effort was made to make POSIX compatible with standard C; POSIX includes additional functions to those introduced in standard C. On the other hand, the 5 headers that were added to the C standard library with C11, were not likewise included in subsequent revisions of POSIX.

It may be included in any C++ project, however the C++ standard library may have its own implementation of certain features, such as <regex> rather than <regex.h>, <thread> rather than <pthread.h>, or <semaphore> rather than <semaphore.h>.