Originální popis anglicky:
sem_getvalue - get the value of a semaphore (
REALTIME)
Návod, kniha: POSIX Programmer's Manual
#include <semaphore.h>
int sem_getvalue(sem_t *restrict
sem, int
*restrict sval);
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.
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.
The
sem_getvalue() function shall fail if:
- EINVAL
- The sem argument does not refer to a valid
semaphore.
The following sections are informative.
None.
The
sem_getvalue() function is part of the Semaphores option and need not
be available on all implementations.
None.
None.
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
.
