POSIX semaphores were created as part of the older 'real-time extensions' aka POSIX.1b, whereas the pthread API was created slightly later as POSIX.1c. (Source

POSIX semaphores were created as part of the older 'real-time extensions' aka POSIX.1b, whereas the pthread API was created slightly later as POSIX.1c. (Source: man pages, plus [1] for a list of standards.) [1] https://man7.org/linux/man-pages/man7/standards.7.html https://man7.org/linux/man-pages/man7/standards.7.html