sem_lock(2) — DG/UX 5.4R2.01



sem_lock(2)                  DG/UX 5.4 Rel. 2.01                 sem_lock(2)


NAME
       sem_lock - lock a semaphore

SYNOPSIS
       #include <semaphore.h>

       int semlock (*sem)
            semt  *sem;

DESCRIPTION
       Use semlock(2) to lock a semaphore, making it unavailable to other
       processes: sem is a valid semaphore descriptor returned by a prior
       seminit(2) call. Once locked, a semaphore stays locked until
       unlocked with semunlock(2). Thus, if your process locks a semaphore
       and then calls semdestroy(2), exit(2), or exec(2), the semaphore
       (provided it continues to exist) remains locked.

       If a semaphore is unavailable, semlock blocks until receiving a
       signal, or until the semaphore becomes available.  For a non-blocking
       lock operation (return immediately with an error if the semaphore is
       unavailable, otherwise lock it), use semtrylock(2).

       Locking a semaphore decrements its value specified with seminit(2)
       and unlocking it increments the value. This call blocks on a 0 or
       negative value, which defines unavailability.

   Note
        * This routine is based on POSIX realtime extension document P1003.4
          draft 12. It is therefore subject to change.

        * Compilation of a source file using this routine requires that
          feature macro _POSIX4_DRAFT_SOURCE be defined.  This feature macro
          is not enabled by any other feature macro, nor does it enable any
          other feature macro.

        * The compiled routine must be linked to library librte.a.

RETURN VALUE
       If successful, semlock returns 0. If unsuccessful, it returns -1 and
       sets ERRNO to one of the following:

        EFAULT *sem is an invalid address.

        EINTR  Woken up by a signal rather than semaphore acquired.

        EINVAL sem is invalid.

        ENOSPC sem is unavailable and there is insufficient memory for
               semlock(2) to block.

SEE ALSO
       semdestroy(2), seminit(2), semtrylock(2), semunlink(2),
       semunlock(2).




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