124 lines
3.3 KiB
Groff
124 lines
3.3 KiB
Groff
.\" Copyright (c) 2002 William C. Fenner. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd October 13, 2002
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.Dt SOCKATMARK 3
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.Os
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.Sh NAME
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.Nm sockatmark
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.Nd determine whether the read pointer is at the OOB mark
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/socket.h
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.Ft int
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.Fn sockatmark "int s"
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.Sh DESCRIPTION
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To find out if the read pointer is currently pointing at
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the mark in the data stream, the
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.Fn sockatmark
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function is provided.
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If
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.Fn sockatmark
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returns 1, the next read will return data
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after the mark.
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Otherwise (assuming out of band data has arrived),
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the next read will provide data sent by the client prior
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to transmission of the out of band signal.
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The routine used
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in the remote login process to flush output on receipt of an
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interrupt or quit signal is shown below.
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It reads the normal data up to the mark (to discard it),
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then reads the out-of-band byte.
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.Bd -literal -offset indent
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#include <sys/socket.h>
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\&...
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oob()
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{
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int out = FWRITE, mark;
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char waste[BUFSIZ];
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/* flush local terminal output */
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ioctl(1, TIOCFLUSH, (char *)&out);
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for (;;) {
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if ((mark = sockatmark(rem)) < 0) {
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perror("sockatmark");
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break;
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}
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if (mark)
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break;
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(void) read(rem, waste, sizeof (waste));
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}
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if (recv(rem, &mark, 1, MSG_OOB) < 0) {
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perror("recv");
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...
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}
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...
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}
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.Ed
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.Sh RETURN VALUES
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Upon successful completion, the
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.Fn sockatmark
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function returns the value 1 if the read pointer is pointing at
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the OOB mark, 0 if it is not.
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Otherwise the value \-1 is returned
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and the global variable
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.Va errno
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is set to
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indicate the error.
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.Sh ERRORS
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The
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.Fn sockatmark
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call fails if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa s
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argument
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is not a valid descriptor.
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.It Bq Er ENOTTY
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The
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.Fa s
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argument
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is a descriptor for a file, not a socket.
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.El
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.Sh SEE ALSO
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.Xr recv 2 ,
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.Xr send 2
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.Sh HISTORY
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The
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.Fn sockatmark
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function was introduced by
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.St -p1003.1-2001 ,
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to standardize the historical
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.Dv SIOCATMARK
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.Xr ioctl 2 .
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The
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.Er ENOTTY
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error instead of the usual
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.Er ENOTSOCK
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is to match the historical behavior of
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.Dv SIOCATMARK .
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