2004-11-03 13:51:07 +00:00
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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2007-06-20 22:33:04 +00:00
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.TH "SEM_GETVALUE" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.\" sem_getvalue
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2007-09-20 06:03:25 +00:00
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.SH PROLOG
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This manual page is part of the POSIX Programmer's Manual.
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The Linux implementation of this interface may differ (consult
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the corresponding Linux manual page for details of Linux behavior),
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or the interface may not be implemented on Linux.
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2004-11-03 13:51:07 +00:00
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.SH NAME
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sem_getvalue \- get the value of a semaphore (\fBREALTIME\fP)
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.SH SYNOPSIS
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.LP
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\fB#include <semaphore.h>
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.br
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.sp
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int sem_getvalue(sem_t *restrict\fP \fIsem\fP\fB, int *restrict\fP
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\fIsval\fP\fB); \fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIsem_getvalue\fP() function shall update the location referenced
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by the \fIsval\fP argument to have the value of the
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semaphore referenced by \fIsem\fP without affecting the state of the
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semaphore. The updated value represents an actual semaphore
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value that occurred at some unspecified time during the call, but
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it need not be the actual value of the semaphore when it is
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returned to the calling process.
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.LP
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If \fIsem\fP is locked, then the object to which \fIsval\fP points
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shall either be set to zero or to a negative number whose
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absolute value represents the number of processes waiting for the
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semaphore at some unspecified time during the call.
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.SH RETURN VALUE
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.LP
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Upon successful completion, the \fIsem_getvalue\fP() function shall
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return a value of zero. Otherwise, it shall return a value
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of -1 and set \fIerrno\fP to indicate the error.
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.SH ERRORS
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.LP
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The \fIsem_getvalue\fP() function shall fail if:
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.TP 7
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.B EINVAL
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The \fIsem\fP argument does not refer to a valid semaphore.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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The \fIsem_getvalue\fP() function is part of the Semaphores option
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and need not be available on all implementations.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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2007-09-20 17:56:19 +00:00
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\fIsemctl\fP(), \fIsemget\fP(), \fIsemop\fP(),
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\fIsem_post\fP(), \fIsem_timedwait\fP(), \fIsem_trywait\fP(),
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2007-09-20 06:11:55 +00:00
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\fIsem_wait\fP(), the Base Definitions volume of
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2004-11-03 13:51:07 +00:00
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IEEE\ Std\ 1003.1-2001, \fI<semaphore.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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