'\" te .\" Copyright (c) 2008, Sun Microsystems, Inc. All Rights Reserved. .\" Copyright 1989 AT&T .\" Portions Copyright (c) 1992, X/Open Company Limited. All Rights Reserved. .\" Sun Microsystems, Inc. gratefully acknowledges The Open Group for permission to reproduce portions of its copyrighted documentation. Original documentation from The Open Group can be obtained online at http://www.opengroup.org/bookstore/. .\" The Institute of Electrical and Electronics Engineers and The Open Group, have given us permission to reprint portions of their documentation. In the following statement, the phrase "this text" refers to portions of the system documentation. Portions of this text are reprinted and reproduced in electronic form in the Sun OS Reference Manual, from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between these versions 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.opengroup.org/unix/online.html. This notice shall appear on any product containing this material. .TH sem_getvalue 3C "5 Feb 2008" "SunOS 5.11" "Standard C Library Functions" .SH NAME sem_getvalue \- get the value of a semaphore .SH SYNOPSIS .LP .nf #include \fBint\fR \fBsem_getvalue\fR(\fBsem_t *restrict\fR \fIsem\fR, \fBint *restrict\fR \fIsval\fR); .fi .SH DESCRIPTION .sp .LP The \fBsem_getvalue()\fR function updates the location referenced by the \fIsval\fR argument to have the value of the semaphore referenced by \fIsem\fR without affecting the state of the semaphore. The updated value represents 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. .sp .LP If \fIsem\fR is locked, then the value returned by \fBsem_getvalue()\fR is either zero or a negative number whose absolute value represents the number of processes waiting for the semaphore at some unspecified time during the call. .sp .LP The value set in \fIsval\fR may be 0 or positive. If \fIsval\fR is 0, there may be other processes (or LWPs or threads) waiting for the semaphore; if \fIsval\fR is positive, no process is waiting. .SH RETURN VALUES .sp .LP Upon successful completion, \fBsem_getvalue()\fR returns \fB0\fR. Otherwise, it returns \fB\(mi1\fR and sets \fBerrno\fR to indicate the error. .SH ERRORS .sp .LP The \fBsem_getvalue()\fR function will fail if: .sp .ne 2 .mk .na \fB\fBEINVAL\fR \fR .ad .RS 11n .rt The \fIsem\fR argument does not refer to a valid semaphore. .RE .sp .ne 2 .mk .na \fB\fBENOSYS\fR \fR .ad .RS 11n .rt The \fBsem_getvalue()\fR function is not supported by the system. .RE .SH ATTRIBUTES .sp .LP See \fBattributes\fR(5) for descriptions of the following attributes: .sp .sp .TS tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) . ATTRIBUTE TYPEATTRIBUTE VALUE _ Interface StabilityCommitted _ MT-LevelMT-Safe _ StandardSee \fBstandards\fR(5). .TE .SH SEE ALSO .sp .LP \fBsemctl\fR(2), \fBsemget\fR(2), \fBsemop\fR(2), \fBsem_post\fR(3C), \fBsem_wait\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)