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


     pthread_join - join with a terminated thread


     #include <pthread.h>
     int pthread_join(pthread_t thread, void **retval);
     Compile and link with -pthread.


     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 the location
     pointed to by 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).


     On  success,  pthread_join()  returns  0; on error, it returns an error


            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.


     For   an   explanation   of   the  terms  used  in  this  section,  see
     |Interface      | Attribute     | Value   |
     |pthread_join() | Thread safety | MT-Safe |


     POSIX.1-2001, POSIX.1-2008.


     After a successful call to pthread_join(),  the  caller  is  guaranteed
     that  the  target thread has terminated.  The caller may then choose to
     do any clean-up that is required after termination of the thread (e.g.,
     freeing  memory  or  other  resources that were allocated to the target
     Joining with a thread that has previously been joined results in  unde-
     fined 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  functional-
     ity, 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.


     See pthread_create(3).


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


     This  page  is  part of release 4.16 of the Linux man-pages project.  A
     description of the project, information about reporting bugs,  and  the
     latest     version     of     this    page,    can    be    found    at

Linux 2017-09-15 PTHREAD_JOIN(3)

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