pthreadjoin

pthread_join is a function in the POSIX threads (pthreads) API that allows one thread to wait for another to finish and to obtain the terminating status of that thread. It is used to synchronize thread completion and to reclaim resources associated with a thread.

Signature and parameters: int pthread_join(pthread_t thread, void retval); The thread parameter specifies the target thread to wait for. If retval is non-NULL, it is set to point to the thread’s exit status value as provided to pthread_exit, or to PTHREAD_CANCELED if the thread was canceled.

Behavior: The calling thread blocks until the specified thread terminates. Upon successful completion, the resources of the terminated thread are released. After a successful join, the thread handle is no longer usable for future joins.

Return values and errors: The function returns 0 on success. On error, it returns an error number, and errno is set accordingly. Common errors include EDEADLK (a deadlock condition was detected or attempting to join the calling thread), EINVAL (the thread is not joinable, for example it was created as detached or has already been joined), and ESRCH (no thread could be found with the given ID).

Usage considerations: A thread must be joinable to be joined. Do not attempt to join a thread more than once and do not join a thread after it has been detached. If you need to reuse a thread’s resources without waiting, consider using pthread_detach. Retrieving the thread’s exit value via retval provides a mechanism to communicate results from the thread.

See also: pthread_exit, pthread_cancel, pthread_detach.