VMS Help DCE_THREADS, Application Routines, pthread_mutex_trylock  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  NAME

      pthread_mutex_trylock - Locks a mutex

  SYNOPSIS

      #include <pthread.h>

      int pthread_mutex_trylock( pthread_mutex_t *mutex );

  PARAMETERS

      mutex                Mutex that is locked.

  DESCRIPTION

  The pthread_mutex_trylock() routine locks a mutex. If the specified
  mutex is locked when a thread calls this routine, the calling thread
  does not wait for the mutex to become available.

  When a thread calls this routine, an attempt is made to lock the mutex
  immediately.  If the mutex is successfully locked, 1 is returned and the
  current thread is then the mutex's current owner.

  If the mutex is locked by another thread when this routine is called, 0
  (zero) is returned and the thread does not wait to acquire the lock.  If
  a fast mutex is owned by the current thread, 0 is returned. If a recur-
  sive mutex is owned by the current thread, 1 is returned and the mutex
  is relocked. (To unlock a recursive mutex, each call to
  pthread_mutex_trylock() must be matched by a call to the
  pthread_mutex_unlock() routine.)

  RETURN VALUES

  If the function fails, errno may be set to one of the following values:

    Return   Error      Description
    ____________________________________________________________
     1                  Successful completion.

     0                  The mutex is  locked; therefore, it was
                        not acquired.

    -1      [EINVAL]    The value specified by mutex is invalid.

  RELATED INFORMATION

      FUNCTIONS:  pthread_mutexattr_setkind_np
                  pthread_mutex_destroy
                  pthread_mutex_init
                  pthread_mutex_lock
                  pthread_mutex_unlock