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SEM_GETVALUE(3P)           POSIX Programmer's Manual          SEM_GETVALUE(3P)
PROLOG
       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
       sem_getvalue -- get the value of a semaphore
SYNOPSIS
       #include <semaphore.h>
       int sem_getvalue(sem_t *restrict sem, int *restrict sval);
DESCRIPTION
       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  repre-
       sents  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
       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
       The sem_getvalue() function may fail if:
       EINVAL The sem argument does not refer to a valid semaphore.
       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       None.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       semctl(), semget(), semop(), sem_post(), sem_timedwait(), sem_trywait()
       The Base Definitions volume of POSIX.1-2008, <semaphore.h>
COPYRIGHT
       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 Electri-
       cal 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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                     SEM_GETVALUE(3P)