Interprocess Communications in Linux®: The Nooks & Crannies By John Shapley Gray Publisher: Prentice Hall PTR Pub Date: January 13, 2003 ISBN: 0-13-046042-7 Copyright Introduction Acknowledgments Chapter 1. Programs and Processes Section 1.1. Introduction Section 1.2. Library Functions Section 1.3. System Calls Section 1.4. Linking Object Code Section 1.5. Managing Failures Section 1.6. Executable File Format Section 1.7. System Memory Section 1.8. Process Memory Section 1.9. The u Area Section 1.10. Process Memory Addresses Section 1.11. Creating a Process Section 1.12. Summary Section 1.13. Key Terms and Concepts Chapter 2. Processing Environment Section 2.1. Introduction Section 2.2. Process ID Section 2.3. Parent Process ID Section 2.4. Process Group ID Section 2.5. Permissions Section 2.6. Real and Effective User and Group IDs Section 2.7. File System Information Section 2.8. File Information Section 2.9. Process Resource Limits Section 2.10. Signaling Processes Section 2.11. Command-Line Values Section 2.12. Environment Variables Section 2.13. The /proc Filesystem Section 2.14. Summary Section 2.15. Key Terms and Concepts Chapter 3. Using Processes Section 3.1. Introduction Section 3.2. The fork System Call Revisited Section 3.3. exec's Minions Section 3.4. Using fork and exec Together Section 3.5. Ending a Process Section 3.6. Waiting on Processes Section 3.7. Summary Section 3.8. Key Terms and Concepts Chapter 4. Primitive Communications Section 4.1. Introduction Section 4.2. Lock Files Section 4.3. Locking Files Section 4.4. More About Signals Section 4.5. Signal and Signal Management Calls Section 4.6. Summary Section 4.7. Key Terms and Concepts Chapter 5. Pipes Section 5.1. Introduction Section 5.2. Unnamed Pipes Section 5.3. Named Pipes Section 5.4. Summary Section 5.5. Key Terms and Concepts Chapter 6. Message Queues Section 6.1. Introduction Section 6.2. IPC System Calls: A Synopsis Section 6.3. Creating a Message Queue Section 6.4. Message Queue Control Section 6.5. Message Queue Operations Section 6.6. A Client?Server Message Queue Example Section 6.7. Message Queue Class Section 6.8. Summary Section 6.9. Key Terms and Concepts Chapter 7. Semaphores Section 7.1. Introduction Section 7.2. Creating and Accessing Semaphore Sets Section 7.3. Semaphore Control Section 7.4. Semaphore Operations Section 7.5. Semaphore Class Section 7.6. Summary Section 7.7. Key Terms and Concepts Chapter 8. Shared Memory Section 8.1. Introduction Section 8.2. Creating a Shared Memory Segment Section 8.3. Shared Memory Control Section 8.4. Shared Memory Operations Section 8.5. Using a File as Shared Memory Section 8.6. Shared Memory Class Section 8.7. Summary Section 8.8. Key Terms and Concepts Chapter 9. Remote Procedure Calls Section 9.1. Introduction Section 9.2. Executing Remote Commands at a System Level Section 9.3. Executing Remote Commands in a Program Section 9.4. Transforming a Local Function Call into a Remote Procedure Section 9.5. Debugging RPC Applications Section 9.6. Using RPCGEN to Generate Templates and aMAKEFILE Section 9.7. Encoding and Decoding Arbitrary Data Types Section 9.8. Using Broadcasting to Search for an RPC Service Section 9.9. Summary Section 9.10. Key Terms and Concepts Chapter 10. Sockets Section 10.1. Introduction Section 10.2. Communication Basics Section 10.3. IPC Using Socketpair Section 10.4. Sockets: The Connection-Oriented Paradigm Section 10.5. Sockets: The Connectionless Paradigm Section 10.6. Multiplexing I/O withselect Section 10.7. Peeking at Data Section 10.8. Out of Band Messages Section 10.9. Summary Section 10.10. Key Terms and Concepts Chapter 11. Threads Section 11.1. Introduction Section 11.2. Creating a Thread Section 11.3. Exiting a Thread Section 11.4. Basic Thread Management Section 11.5. Thread Attributes Section 11.6. Scheduling Threads Section 11.7. Using Signals in Threads Section 11.8. Thread Synchronization Section 11.9. Thread-Specific Data Section 11.10. Debugging Multithreaded Programs Section 11.11. Summary Section 11.12. Nomenclature and Key Concepts Appendix A. Using Linux Manual Pages Section A.1. Manual Page Sections Section A.2. Manual Page Format Section A.3. Standard Linux System Calls Appendix B. UNIX Error Messages Appendix C. RPC Syntax Diagrams Section C.1. Introduction Section C.2. RPC Definitions Section C.3. RPC Keywords Section C.4. Some RPC Examples Appendix D. Profiling Programs Section D.1. Introduction Section D.2. Sample Program for Profiling Section D.3. Generating Profile Data Section D.4. Viewing and Interpreting Profile Data Appendix E. Bibliography Top Copyright Library of Congress Cataloging-in-Publication available Editorial/production supervision: Kathleen M. Caren Executive Editor: Greg Doench Editorial Assistant: Brandt Kenna Marketing Manager: Debby vanDijk Manufacturing Manager: Alexis Heydt-Long Cover Design Director: Jerry Votta Composition: G&S Typesetters, Inc. © 2003 Pearson Education Inc. Publishing as Prentice Hall PTR Upper Saddle River, NJ 07458 Prentice Hall books are widely used by corporations and government agencies for training, marketing, and resale. For information regarding corporate and government bulk discounts, contact: Corporate and Government Sales: (800) 382-3419 or [email protected] All products mentioned herein are trademarks or registered trademarks of their respective owners. All rights reserved. No part of this book may be reproduced, in any form or by any means, without permission in writing from the publisher. Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 Pearson Education LTD. Pearson Education Australia PTY, Limited Pearson Education Singapore, Pte. Ltd. Pearson Education North Asia Ltd. Pearson Education Canada, Ltd. Pearson Educación de Mexico, S.A. de C.V. Pearson Education—Japan Pearson Education Malaysia, Pte. Ltd. Dedication To my wife, Marie Top Introduction The topic of interprocess communication techniques is broad, challenging and dynamic. All but the most basic operating systems provide methods for processes communication. Early on, UNIX supported a number of rudimentary process communication constructs (such as lock files, signals and pipes). In the early 1980s, facilities such as message queues, semaphores, and shared memory were added to the mix by AT&T with its release of UNIX System V. Somewhat concurrently, the Berkeley Software Distribution added support for Internet protocols (4.3BSD) and the socket interface as a communication construct. By the mid-1990s, threads and multithreaded programming techniques were making significant, permanent inroads into the UNIX mainstream. Along the way, UNIX spawned innumerable UNIX-like operating systems. One such operating system was MINIX. MINIX, written by Andrew S. Tanenbaum, is a small (about twelve thousand lines) PC version of UNIX. MINIX was presented as a pedagogical tool to permit the user to gain a better understanding of the inner working of a UNIX-like operating system. As all of the operating system source code was provided, the user could tinker with the code and refine its functionality. As a university student, Linus Torvalds' exposure to MINIX led him to develop a more robust UNIX-like operating system called Linux. In brief, Linux is a freely distributed hybrid version of UNIX. Linux system administration is BSD-like while its programming environment has a definite AT&T flavor. A number of commercial versions of Linux populate the market. These versions bundle Linux with a variety of other operating system related utilities and software packages. One of the more widely distributed commercial versions is Red Hat Linux. Red Hat Linux includes Richard Stallman's GNU project C (gcc) and C++ (g++) compilers. This text explores the intricacies of interprocess communications as supported by Red Hat Linux version 7.3 and 8.0. It is assumed that the reader has a working knowledge of C/C++ programming. It is further assumed that while not being an expert, the reader has worked in a UNIX type environment and is reasonably familiar with generating and editing text using an editor such as vi or pico (available from the University of Washington). This text makes extensive references to specific system calls and predefined library functions. The reader is encouraged to read the manual pages for each system call/library function as it is encountered. As in UNIX, the manual pages in Linux are an unparalleled source of information. Appendix A covers the format and use of manual pages. All programming references and examples were generated on a PC Pentium-based platform running Red Hat Linux 7.3, using the GNU C/C++ compiler version 2.96. With the release of Red Hat Linux 8.0 and GNU 3.2 the examples were revisited and tweaked where necessary. Many of the examples and most of the exercises have also been compiled and run in a Solaris 2.8 setting using GNU 2.95. Most often, few if any modifications were needed to generate clean, executable code in this alternate environment. Each example is a complete standalone program. Command line examples, except where noted, are Korn shell based. In any setting, IPC (interprocess communication) support must be available for the user to pursue the materials covered in the chapters on semaphores, message queues, and shared memory. When Linux is installed, usually IPC support is enabled (check the /proc directory for the presence of the sysvipc directory). If it is not present you may need to modify system configuration files and recompile the kernel. There are a number of places that one can peruse for information on how this might be done. One source of information is the Configure.help file that resides in the /usr/src/linuxXXXX/Documentation subdirectory (where XXXX is the version of Linux).