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)

PROLOG         top

       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.

NAME         top

       sem_getvalue — get the value of a semaphore

SYNOPSIS         top

       #include <semaphore.h>

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

DESCRIPTION         top

       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         top

       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         top

       The sem_getvalue() function may fail if:

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

       The following sections are informative.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       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)

COPYRIGHT         top

       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)