sem_getvalue(3p) — Linux manual page

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.1‐2017, semaphore.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 .

       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                2017                  SEM_GETVALUE(3P)

Pages that refer to this page: semaphore.h(0p),  semctl(3p),  semget(3p),  semop(3p)

HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH.