1SEM_GETVALUE(3P)           POSIX Programmer's Manual          SEM_GETVALUE(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

13       sem_getvalue — get the value of a semaphore
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SYNOPSIS

16       #include <semaphore.h>
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18       int sem_getvalue(sem_t *restrict sem, int *restrict sval);
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DESCRIPTION

21       The sem_getvalue() function shall update the location referenced by the
22       sval  argument  to  have  the  value of the semaphore referenced by sem
23       without affecting the state of the semaphore. The updated value  repre‐
24       sents  an actual semaphore value that occurred at some unspecified time
25       during the call, but it need not be the actual value of  the  semaphore
26       when it is returned to the calling process.
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28       If  sem is locked, then the object to which sval points shall either be
29       set to zero or to a negative number whose absolute value represents the
30       number  of processes waiting for the semaphore at some unspecified time
31       during the call.
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RETURN VALUE

34       Upon successful completion, the sem_getvalue() function shall return  a
35       value  of  zero. Otherwise, it shall return a value of −1 and set errno
36       to indicate the error.
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ERRORS

39       The sem_getvalue() function may fail if:
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41       EINVAL The sem argument does not refer to a valid semaphore.
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43       The following sections are informative.
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EXAMPLES

46       None.
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APPLICATION USAGE

49       None.
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RATIONALE

52       None.
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FUTURE DIRECTIONS

55       None.
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SEE ALSO

58       semctl(), semget(), semop(), sem_post(), sem_timedwait(), sem_trywait()
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60       The Base Definitions volume of POSIX.1‐2008, <semaphore.h>
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63       Portions of this text are reprinted and reproduced in  electronic  form
64       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
65       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
66       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
67       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
68       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) In the
69       event of any discrepancy between this version and the original IEEE and
70       The  Open Group Standard, the original IEEE and The Open Group Standard
71       is the referee document. The original Standard can be  obtained  online
72       at http://www.unix.org/online.html .
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74       Any  typographical  or  formatting  errors that appear in this page are
75       most likely to have been introduced during the conversion of the source
76       files  to  man page format. To report such errors, see https://www.ker‐
77       nel.org/doc/man-pages/reporting_bugs.html .
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81IEEE/The Open Group                  2013                     SEM_GETVALUE(3P)
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