pthread_join(3)

1PTHREAD_JOIN(3)            Linux Programmer's Manual           PTHREAD_JOIN(3)
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NAME

6       pthread_join - join with a terminated thread
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SYNOPSIS

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

16       The pthread_join() function waits for the thread specified by thread to
17       terminate.  If that thread has already terminated, then  pthread_join()
18       returns immediately.  The thread specified by thread must be joinable.
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20       If  retval  is  not NULL, then pthread_join() copies the exit status of
21       the target thread (i.e., the value that the target thread  supplied  to
22       pthread_exit(3))  into the location pointed to by *retval.  If the tar‐
23       get thread was canceled, then PTHREAD_CANCELED is placed in *retval.
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25       If multiple threads simultaneously try to join with  the  same  thread,
26       the  results  are  undefined.   If the thread calling pthread_join() is
27       canceled, then the target thread will remain joinable  (i.e.,  it  will
28       not be detached).
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RETURN VALUE

31       On  success,  pthread_join()  returns  0; on error, it returns an error
32       number.
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ERRORS

35       EDEADLK
36              A deadlock was detected (e.g., two threads tried  to  join  with
37              each other); or thread specifies the calling thread.
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39       EINVAL thread is not a joinable thread.
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41       EINVAL Another thread is already waiting to join with this thread.
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43       ESRCH  No thread with the ID thread could be found.
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CONFORMING TO

46       POSIX.1-2001.
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NOTES

49       After  a  successful  call  to pthread_join(), the caller is guaranteed
50       that the target thread has terminated.
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52       Joining with a thread that has previously been joined results in  unde‐
53       fined behavior.
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55       Failure  to  join with a thread that is joinable (i.e., one that is not
56       detached), produces a "zombie thread".  Avoid doing  this,  since  each
57       zombie  thread  consumes  some system resources, and when enough zombie
58       threads have accumulated, it will no longer be possible to  create  new
59       threads (or processes).
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61       There  is no pthreads analog of waitpid(-1, &status, 0), that is, "join
62       with any terminated thread".  If you believe you need this  functional‐
63       ity, you probably need to rethink your application design.
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65       All of the threads in a process are peers: any thread can join with any
66       other thread in the process.
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EXAMPLE

69       See pthread_create(3).
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COLOPHON

76       This  page  is  part of release 3.53 of the Linux man-pages project.  A
77       description of the project, and information about reporting  bugs,  can
78       be found at http://www.kernel.org/doc/man-pages/.
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82Linux                             2008-11-27                   PTHREAD_JOIN(3)