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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 terminated, 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

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