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NAME
       sem_getvalue - get the value of a semaphore (REALTIME)


SYNOPSIS
       #include <semaphore.h>

       int sem_getvalue(sem_t *restrict sem, int *restrict sval);


DESCRIPTION
       The  sem_getvalue()  function shall update the location referenced by the sval argument to have the value
       of the semaphore referenced by sem without affecting the  state  of  the  semaphore.  The  updated  value
       represents  an actual semaphore value that occurred at some unspecified time during the call, but it need
       not be the actual value of the semaphore when it is returned to the calling process.

       If sem is locked, then the object to which sval points shall either be set  to  zero  or  to  a  negative
       number  whose  absolute  value  represents  the  number  of  processes  waiting for the semaphore at some
       unspecified time during the call.


RETURN VALUE
       Upon successful completion, the sem_getvalue() function shall return a value of zero. Otherwise, it shall
       return a value of -1 and set errno to indicate the error.


ERRORS
       The sem_getvalue() function shall fail if:

       EINVAL The sem argument does not refer to a valid semaphore.

       The following sections are informative.


EXAMPLES
       None.


APPLICATION USAGE
       The  sem_getvalue()  function  is  part  of  the  Semaphores  option  and  need  not  be available on all
       implementations.


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       semctl() , semget() , semop() , sem_post() , sem_timedwait() , sem_trywait()  ,  sem_wait()  ,  the  Base
       Definitions volume of IEEE Std 1003.1-2001, <semaphore.h>


       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc and The Open Group. In the event of any discrepancy between this version and the  original  IEEE  and
       The  Open  Group  Standard,  the  original  IEEE and The Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .