Return_Values

   0                  Successful completion. The function executes
                      the semaphore lock operation.
   -1                 Indicates an error. The function sets errno to
                      one of the following values:

                      o  ETIMEDOUT - The semaphore could not
                         be locked before the specified timeout
                         expired.

                      o  EINVAL - The sem argument does not refer to
                         a valid semaphore. Or the process or thread
                         would have blocked, and the abs_timeout
                         parameter specified a nanoseconds field
                         value less than zero or greater than or
                         equal to 1000 million.

                      o  EVMSERR - OpenVMS specific nontranslatable
                         error code.