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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
SEM_GETVALUE(3P) POSIX Programmer's Manual SEM_GETVALUE(3P)
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
sem_getvalue — get the value of a semaphore
#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 may fail if:
EINVAL The sem argument does not refer to a valid semaphore.
The following sections are informative.
None.
None.
None.
None.
semctl(3p), semget(3p), semop(3p), sem_post(3p), sem_timedwait(3p),
sem_trywait(3p)
The Base Definitions volume of POSIX.1‐2008, semaphore.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 SEM_GETVALUE(3P)
Pages that refer to this page: semaphore.h(0p), semctl(3p), semget(3p), semop(3p)