pthread_join(3) - Linux manual page (original) (raw)

pthreadjoin(3) Library Functions Manual pthreadjoin(3)

NAME top

   pthread_join - join with a terminated thread

LIBRARY top

   POSIX threads library (_libpthread_, _-lpthread_)

SYNOPSIS top

   **#include <pthread.h>**

   **int pthread_join(pthread_t** _thread_**, void** _retval_**);**

DESCRIPTION top

   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)](../man3/pthread%5Fexit.3.html)) 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).

RETURN VALUE top

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

ERRORS top

   **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.

ATTRIBUTES top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌──────────────────────────────────────┬───────────────┬─────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├──────────────────────────────────────┼───────────────┼─────────┤
   │ **pthread_join**()                       │ Thread safety │ MT-Safe │
   └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

   POSIX.1-2008.

HISTORY top

   POSIX.1-2001.

NOTES top

   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 thread).

   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.

EXAMPLES top

   See [pthread_create(3)](../man3/pthread%5Fcreate.3.html).

SEE ALSO top

   [pthread_cancel(3)](../man3/pthread%5Fcancel.3.html), [pthread_create(3)](../man3/pthread%5Fcreate.3.html), [pthread_detach(3)](../man3/pthread%5Fdetach.3.html),
   [pthread_exit(3)](../man3/pthread%5Fexit.3.html), [pthread_tryjoin_np(3)](../man3/pthread%5Ftryjoin%5Fnp.3.html), [pthreads(7)](../man7/pthreads.7.html)

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Linux man-pages 6.10 2024-07-23 pthreadjoin(3)

Pages that refer to this page:pthread_attr_setdetachstate(3), pthread_cancel(3), pthread_create(3), pthread_detach(3), pthread_exit(3), pthread_tryjoin_np(3)