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