1SEM_GETVALUE(3P) POSIX Programmer's Manual SEM_GETVALUE(3P)
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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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12 sem_getvalue — get the value of a semaphore
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15 #include <semaphore.h>
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17 int sem_getvalue(sem_t *restrict sem, int *restrict sval);
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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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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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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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45 None.
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48 None.
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51 None.
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54 None.
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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)