pthread_join - join with a terminated thread
int pthread_join(pthread_t thread, void **retval);
Compile and link with -pthread
() function waits for the thread specified by
to terminate. If that thread has already terminated, then
() returns immediately. The thread specified by
must be joinable.
is not NULL, then pthread_join
() copies the exit status
of the target thread (i.e., the value that the target thread supplied to
(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.
- thread is not a joinable thread.
- Another thread is already waiting to join with this thread.
- No thread with the ID thread could be found.
For an explanation of the terms used in this section, see attributes
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
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
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.