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diff --git a/share/doc/psd/21.ipc/1.t b/share/doc/psd/21.ipc/1.t new file mode 100644 index 00000000000..f4e48ffc23d --- /dev/null +++ b/share/doc/psd/21.ipc/1.t @@ -0,0 +1,106 @@ +.\" Copyright (c) 1986, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)1.t 8.1 (Berkeley) 8/14/93 +.\" +.\".ds LH "4.4BSD IPC Primer +.\".ds RH Introduction +.\".ds RF "Leffler/Fabry/Joy +.\".ds LF "\*(DY +.\".ds CF " +.nr H1 1 +.LP +.bp +.LG +.B +.ce +1. INTRODUCTION +.sp 2 +.R +.NL +One of the most important additions to UNIX in 4.2BSD was interprocess +communication. +These facilities were the result of +more than two years of discussion and research. The facilities +provided in 4.2BSD incorporated many of the ideas from current +research, while trying to maintain the UNIX philosophy of +simplicity and conciseness. +The 4.3BSD release of Berkeley UNIX +improved upon some of the IPC facilities +while providing an upward-compatible interface. +4.4BSD adds support for ISO protocols and IP multicasting. +The BSD interprocess communication +facilities have become a defacto standard for UNIX. +.PP +UNIX has previously been very weak in the area of interprocess +communication. Prior to the 4BSD facilities, the only +standard mechanism which allowed two processes to communicate were +pipes (the mpx files which were part of Version 7 were +experimental). Unfortunately, pipes are very restrictive +in that +the two communicating processes must be related through a +common ancestor. +Further, the semantics of pipes makes them almost impossible +to maintain in a distributed environment. +.PP +Earlier attempts at extending the IPC facilities of UNIX have +met with mixed reaction. The majority of the problems have +been related to the fact that these facilities have been tied to +the UNIX file system, either through naming or implementation. +Consequently, the IPC facilities provided in 4.2BSD were +designed as a totally independent subsystem. The BSD IPC +allows processes to rendezvous in many ways. +Processes may rendezvous through a UNIX file system-like +name space (a space where all names are path names) +as well as through a +network name space. In fact, new name spaces may +be added at a future time with only minor changes visible +to users. Further, the communication facilities +have been extended to include more than the simple byte stream +provided by a pipe. These extensions have resulted +in a completely new part of the system which users will need +time to familiarize themselves with. It is likely that as +more use is made of these facilities they will be refined; +only time will tell. +.PP +This document provides a high-level description +of the IPC facilities in 4.4BSD and their use. +It is designed to complement the manual pages for the IPC primitives +by examples of their use. +The remainder of this document is organized in four sections. +Section 2 introduces the IPC-related system calls and the basic model +of communication. Section 3 describes some of the supporting +library routines users may find useful in constructing distributed +applications. Section 4 is concerned with the client/server model +used in developing applications and includes examples of the +two major types of servers. Section 5 delves into advanced topics +which sophisticated users are likely to encounter when using +the IPC facilities. |