'\" te
.\"  Copyright 1989 AT&T
.\" Copyright (c) 2006, Sun Microsystems, Inc.
.\"  All Rights Reserved
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.TH backq 9F "16 Jan 2006" "SunOS 5.11" "Kernel Functions for Drivers"
.SH NAME
backq \- get pointer to the queue behind the current queue
.SH SYNOPSIS
.LP
.nf
#include <sys/stream.h> 



\fBqueue_t *\fR\fBbackq\fR(\fBqueue_t *\fR\fIcq\fR);
.fi

.SH INTERFACE LEVEL
.sp
.LP
Architecture independent level 1 (DDI/DKI).
.SH PARAMETERS
.sp
.ne 2
.mk
.na
\fB\fIcq\fR\fR
.ad
.RS 6n
.rt  
The pointer to the current queue.   \fBqueue_t\fR is an alias for the
\fBqueue\fR(9S) structure.
.RE

.SH DESCRIPTION
.sp
.LP
The \fBbackq()\fR function returns a pointer to the queue preceding \fIcq\fR
(the current queue). If \fIcq\fR is a read queue, \fBbackq()\fR returns a
pointer to the queue downstream from \fIcq\fR, unless it is the stream end. If
\fIcq\fR is a write queue, \fBbackq()\fR returns a pointer to the next queue
upstream from \fIcq\fR, unless it is the stream head.
.SH RETURN VALUES
.sp
.LP
If successful, \fBbackq()\fR returns a pointer to the queue preceding the
current queue. Otherwise, it returns \fINULL.\fR
.SH CONTEXT
.sp
.LP
The \fBbackq()\fR function can be called from user, interrupt, or kernel
context.
.SH SEE ALSO
.sp
.LP
\fBqueue\fR(9S)
.sp
.LP
\fIWriting Device Drivers\fR
.sp
.LP
\fISTREAMS Programming Guide\fR