84 lines
3.8 KiB
Perl
84 lines
3.8 KiB
Perl
.\" Copyright (c) 1983, 1993
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.\" The Regents of the University of California. 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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND 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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.\" @(#)2.0.t 8.1 (Berkeley) 6/8/93
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.\"
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.ds ss 1
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.sh "System facilities
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This section discusses the system facilities that
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are not considered part of the kernel.
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.PP
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The system abstractions described are:
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.IP "Directory contexts
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.br
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A directory context is a position in the UNIX file system name
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space. Operations on files and other named objects in a file system are
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always specified relative to such a context.
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.IP "Files
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.br
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Files are used to store uninterpreted sequence of bytes on which
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random access \fIreads\fP and \fIwrites\fP may occur.
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Pages from files may also be mapped into process address space.\(dg
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A directory may be read as a file.
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.FS
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\(dg Support for mapping files is not included in the 4.3 release.
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.FE
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.IP "Communications domains
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.br
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A communications domain represents
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an interprocess communications environment, such as the communications
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facilities of the UNIX system,
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communications in the INTERNET, or the resource sharing protocols
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and access rights of a resource sharing system on a local network.
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.IP "Sockets
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.br
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A socket is an endpoint of communication and the focal
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point for IPC in a communications domain. Sockets may be created in pairs,
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or given names and used to rendezvous with other sockets
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in a communications domain, accepting connections from these
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sockets or exchanging messages with them. These operations model
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a labeled or unlabeled communications graph, and can be used in a
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wide variety of communications domains. Sockets can have different
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\fItypes\fP\| to provide different semantics of communication,
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increasing the flexibility of the model.
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.IP "Terminals and other devices
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.br
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Devices include
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terminals, providing input editing and interrupt generation
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and output flow control and editing, magnetic tapes,
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disks and other peripherals. They often support the generic
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\fIread\fP and \fIwrite\fP operations as well as a number of \fIioctl\fP\|s.
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.IP "Processes
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.br
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Process descriptors provide facilities for control and debugging of
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other processes.
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.ds ss 2
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