pthread_rwlock_trywrlock( ) function shall apply a write lock like the pthread_rwlock_wrlock( ) function, with the exception that the function shall fail if any thread currently holds rwlock (for reading or writing) The pthread_rwlock_trywrlock( ) function shall return zero if the lock for writing on the read-write lock object referenced by rwlock is acquired. Otherwise, an error number shall be returned to indicate the error. The pthread_rwlock_trywrlock( ) function shall fail if: [EBUSY] The read-write lock could not be acquired for writing because a writer holds the lock or a writer with the appropriate priority was blocked on it. It may fail if: [EINVAL] rwlock does not refer to an initialized read-write lock object It shall not return EINTR.