sem_getvalue(2) — DG/UX R4.11MU05



sem_getvalue(2)                DG/UX R4.11MU05               sem_getvalue(2)


NAME
       sem_getvalue - get the current value of a semaphore

SYNOPSIS
       #include <semaphore.h>

       int semgetvalue (*sem, *semaphorevalue)
            semt  *sem;
            int    *semaphorevalue;

DESCRIPTION
       Use semgetvalue(2) to get the current value of a semaphore:

        sem    is a valid semaphore address returned by a prior seminit(2)
               or semopen(2) call.

        semaphorevalue
               is the location to update with the value of the semaphore.

       semgetvalue updates the location referenced by the semaphorevalue
       argument to have the value of the semaphore referenced by sem,
       without affecting the state of the semaphore.

       The semaphorevalue returned is an actual semaphore value which
       occurred at some unspecified time during the call, but may not be the
       actual value of the semaphore when it is returned to the calling
       process.

       If sem is locked and unavailable to other processes, then the
       semaphorevalue returned by semgetvalue is zero.  If the semaphore
       is unlocked and available to other processes (semtrywait(2) will
       successfully return), then the semaphorevalue returned by
       semgetvalue is positive, and represents the number of successful
       semtrywait(2) calls that can be done on the semaphore.

   Note
        * This routine is based on POSIX realtime extension document P1003.4
          draft 14. 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, semgetvalue returns 0. If unsuccessful, it returns -1
       and sets ERRNO to one of the following:

        EINVAL sem is invalid.

SEE ALSO
       semdestroy(2), semclose(2), seminit(2), semopen(2),
       semtrywait(2), semwait(2), semunlink(2), sempost(2).


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