The function int pthread_condattr_getclock(pthread_condattr_t *restrict attr, clockid_t *restrict clock_id); shall get the 'clock' attribute from an attributes object referenced by 'attr'. It will store the value of the clock attribute into clock_id and return 0. It returns 0 upon success, and an error code if it fails: It may fail if: [EINVAL] - the 'attr' value is invalid