The int pthread_create(pthread_t *restrict thread, const pthread_attr_t *restrict attr, void *(*start_routine) (void*), void *restrict arg); creates a new thread, with attributes specified by 'attr', within a process. If 'attr' is NULL, the default attributes shall be used. The attribute that will be tested is the detached state, because that is the only state that has a default listed in the specification. default: PTHREAD_CREATE_JOINABLE Other valid values: PTHREAD_CREATE_DETACHED If the attributes specified by 'attr' are modified later after the thread is create, the thread's attributes should not be affected. If success, pthread_create() will store the ID of the the created thread in the location referenced by 'thread'. The thread is created executing 'start_routine' with 'arg' as its only argument. If the 'start_routine' returns, the effect shall be as if there was an implicit call to pthread_exit() using the return value of 'start_routine' as the exit status. NOTE: that the thread in which main() was originally invoked is different from this When it returns from main(), the effect shall be as if there was an implicit call to exit() using the return value of main() as the exit status. The signal state of the new thread will be initialized as so: - The signal mask shall be inherited from the created thread - The set of signals pending for the new thread shall be empty. The floating point environment shall be inherited from the created thread. If pthread_create() fails, no new thread is created and the contents of the location referenced by 'thread' is undefined. if _POSIX_THREAD_CPUTIME is defined, the new thread shall have a CPU-time clock accessible, and the initial value of this clock shall be set to 0. If success, pthread_create() returns zero. If pthread_create() fails, an error number is returned: - [EAGAIN] The system lacked the resources to create another thread, or the system-imposed limit on the total number of threads in a process {PTHREAD_THREADS_MAX} would be exceeded. - [EINVAL] The value specified by 'attr' is invalid. - [EPERM] The caller does not have the appropriate permission to set the required scheduling parameters or scheduling policy. [EINTR] must not be returned. If the current thread uses an alternate stack, the new thread does not inherit this stack.