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sem_getvalue(3p) — Linux manual page

SEM_GETVALUE(3P)        POSIX Programmer's ManualSEM_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 *restrictsem, int *restrictsval);

DESCRIPTION        top

       Thesem_getvalue() function shall update the location referenced       by thesval argument to have the value of the semaphore referenced       bysem 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.       Ifsem is locked, then the object to whichsval 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, thesem_getvalue() function shall       return a value of zero. Otherwise, it shall return a value of -1       and seterrno to indicate the error.

ERRORS        top

       Thesem_getvalue() function may fail if:EINVALThesem 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 athttp://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, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group                2017SEM_GETVALUE(3P)

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

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