Performs a semaphore lock.

    This function is supported on OpenVMS Integrity servers and
    Alpha only.

    Format

      #include  <semaphore.h>

      #include  <time.h>

      int sem_timedwait  (sem_t *sem, const struct timespec
                         *abs_timeout);

1  –  Argument

 sem

    The semaphore to be locked.

 abs_timeout

    The absolute time after which the timeout expires.

2  –  Description

    The sem_timedwait function locks the semaphore referenced by
    sem as in the sem_wait function. But if the semaphore cannot be
    locked without waiting for another process or thread to unlock
    the semaphore by performing a sem_post function, this wait
    terminates when the specified timeout expires.

    The timeout expires when the absolute time specified by abs_
    timeout passes, as measured by the clock on which timeouts are
    based (that is, when the value of that clock equals or exceeds
    abs_timeout, or if the absolute time specified by abs_timeout has
    already been passed at the time of the call.

    The function will not fail with a timeout if the semaphore can be
    locked immediately. The validity of abs_timeout does not need to
    be checked if the semaphore can be locked immediately.

3  –  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.