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>

COPYRIGHT

       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 .

IEEE/The Open Group                                   2003                                       SEM_GETVALUE(P)