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

12       sem_getvalue — get the value of a semaphore
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SYNOPSIS

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

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

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

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

45       None.
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APPLICATION USAGE

48       None.
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RATIONALE

51       None.
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FUTURE DIRECTIONS

54       None.
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SEE ALSO

57       semctl(), semget(), semop(), sem_post(), sem_timedwait(), sem_trywait()
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59       The Base Definitions volume of POSIX.1‐2017, <semaphore.h>
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62       Portions of this text are reprinted and reproduced in  electronic  form
63       from  IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
64       table Operating System Interface (POSIX), The Open Group Base  Specifi‐
65       cations  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of
66       Electrical and Electronics Engineers, Inc and The Open Group.   In  the
67       event of any discrepancy between this version and the original IEEE and
68       The Open Group Standard, the original IEEE and The Open Group  Standard
69       is  the  referee document. The original Standard can be obtained online
70       at http://www.opengroup.org/unix/online.html .
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72       Any typographical or formatting errors that appear  in  this  page  are
73       most likely to have been introduced during the conversion of the source
74       files to man page format. To report such errors,  see  https://www.ker‐
75       nel.org/doc/man-pages/reporting_bugs.html .
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79IEEE/The Open Group                  2017                     SEM_GETVALUE(3P)
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