PTHREAD_JOIN(3)                                     Linux Programmer's Manual                                    PTHREAD_JOIN(3)



NAME
       pthread_join - join with a terminated thread

SYNOPSIS
       #include <pthread.h>

       int pthread_join(pthread_t thread, void **retval);

       Compile and link with -pthread.

DESCRIPTION
       The  pthread_join()  function  waits  for the thread specified by thread to terminate.  If that thread has already termi-
       nated, then pthread_join() returns immediately.  The thread specified by thread must be joinable.

       If retval is not NULL, then pthread_join() copies the exit status of the target thread (i.e., the value that  the  target
       thread  supplied  to  pthread_exit(3))  into the location pointed to by *retval.  If the target thread was canceled, then
       PTHREAD_CANCELED is placed in *retval.

       If multiple threads simultaneously try to join with the same thread, the results are undefined.  If  the  thread  calling
       pthread_join() is canceled, then the target thread will remain joinable (i.e., it will not be detached).

RETURN VALUE
       On success, pthread_join() returns 0; on error, it returns an error number.

ERRORS
       EDEADLK
              A deadlock was detected (e.g., two threads tried to join with each other); or thread specifies the calling thread.

       EINVAL thread is not a joinable thread.

       EINVAL Another thread is already waiting to join with this thread.

       ESRCH  No thread with the ID thread could be found.

CONFORMING TO
       POSIX.1-2001.

NOTES
       After a successful call to pthread_join(), the caller is guaranteed that the target thread has terminated.

       Joining with a thread that has previously been joined results in undefined behavior.

       Failure to join with a thread that is joinable (i.e., one that is not detached), produces a "zombie thread".  Avoid doing
       this, since each zombie thread consumes some system resources, and when enough zombie threads have accumulated,  it  will
       no longer be possible to create new threads (or processes).

       There  is  no pthreads analog of waitpid(-1, &status, 0), that is, "join with any terminated thread".  If you believe you
       need this functionality, you probably need to rethink your application design.

       All of the threads in a process are peers: any thread can join with any other thread in the process.

EXAMPLE
       See pthread_create(3).

SEE ALSO
       pthread_cancel(3), pthread_create(3), pthread_detach(3), pthread_exit(3), pthread_tryjoin_np(3), pthreads(7)

COLOPHON
       This page is part of release 3.25 of the Linux man-pages project.  A description of the project,  and  information  about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                                                      2008-11-27                                            PTHREAD_JOIN(3)