Advanced Linux Programming Contents At a Glance I Advanced UNIX Programming with Linux 1 Getting Started 3 2 Writing Good GNU/Linux Software 17 3 Processes 45 4 Threads 61 5 Interprocess Communication 95 II Mastering Linux 6 Devices 129 7 The /proc File System 147 8 Linux System Calls 167 9 Inline Assembly Code 189 10 Security 197 11 A Sample GNU/Linux Application 219 III Appendixes A Other Development Tools 259 B Low-Level I/O 281 C Table of Signals 301 D Online Resources 303 E Open Publication License Version 1.0 305 F GNU General Public License 309 Advanced Linux Programming Mark Mitchell, Jeffrey Oldham, and Alex Samuel New Riders www.newriders.com 201 West 103rd Street, Indianapolis, Indiana 46290 An Imprint of Pearson Education Boston ??? Indianapolis ??? London ??? Munich ??? New York ??? San Francisco Advanced Linux Programming Copyright ?? 2001 by New Riders Publishing FIRST EDITION: June, 2001 All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission from the publisher, except for the inclusion of brief quotations in a review. International Standard Book Number: 0-7357-1043-0 Library oi Congress Catalog Card Number: 00-105343 05 04 03 02 01 7 6 5 4 3 2 1 Interpretation of the printing code: The rightmost double- digit number is the year of the book's printing; the right- most single-digit number is the number of the book's printing. For example, the printing code 01-1 shows that the first printing of the book occurred in 2001. Composed in Bembo and MCPdigital by New Riders Publishing. Printed in the United States of America. Trademarks All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capital- ized. New Riders Publishing cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. PostScript is a trademark of Adobe Systems, Inc. Linux is a trademark of Linus Torvalds. Warning and Disclaimer This book is designed to provide information about Advanced Linux Programming. Every effort has been made to make this book as complete and as accurate as possible, but no warranty or fitness is implied. The information is provided on an as-is basis. The authors and New Riders Publishing shall have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this book or from the use of the discs or programs that may accompany it. Publisher David Dwyer Associate Publisher AlValvano Executive Editor Stephanie Wall Managing Editor Gina Brown Acquisitions Editor Ann Quinn Development Editor Laura Loveall Product Marketing Manager Stephanie Layton Publicity Manager Susan Petro Project Editor Caroline Wise Copy Editor Krista Hansing Senior Indexer Cheryl Lenser Manufacturing Coordinator Jim Conway Book Designer Louisa Klucznik Cover Designer Brainstorm Design, Inc. Cover Production Aren Howell Proofreader Debra Neel Composition Amy Parker Table of Contents I Advanced UNIX Programming with Linux 1 1 Getting Started 3 1.1 Editing with Emacs 4 1.2 Compiling with GCC 6 1.3 Automating the Process with GNU Make 9 1.4 Debugging with GNU Debugger (GDB) 11 1.5 Finding More Information 13 2 Writing Good GNU/Linux Software 17 2.1 Interaction With the Execution Environment 17 2.2 Coding Defensively 30 2.3 Writing and Using Libraries 36 3 Processes 45 3.1 Looking at Processes 45 3.2 Creating Processes 48 3.3 Signals 52 3.4 Process Termination 55 4 Threads 61 4.1 Thread Creation 62 4.2 Thread Cancellation 69 4.3 Thread-Specific Data 72 4.4 Synchronization and Critical Sections 77 4.5 GNU/Linux Thread Implementation 92 4.6 Processes Vs. Threads 94 Contents vii 5 Interprocess Communication 95 5.1 Shared Memory 96 5.2 Processes Semaphores 101 5.3 Mapped Memory 105 5.4 Pipes 110 5.5 Sockets 116 II Mastering Linux 127 6 Devices 129 6.1 Device Types 130 6.2 Device Numbers 130 6.3 Device Entries 131 6.4 Hardware Devices 133 6.5 Special Devices 136 6.6 PTYs 142 6.7 hat 144 7 The /proc File System 147 7.1 Extracting Information from /proc 148 7.2 Process Entries 150 7.3 Hardware Information 158 7.4 Kernel Information 160 7.5 Drives, Mounts, and File Systems 161 7.6 System Statistics 165 8 Linux System Calls 167 8.1 Using strace 168 8.2 access: Testing File Permissions 169 8.3 fcnth Locks and Other File Operations 171 8.4 fsync and fdatasync: Flushing Disk Buffers 173 8.5 getrlimit and setrlimit. Resource Limits 174 8.6 getmsage: Process Statistics 175 8.7 gettimeofday: Wall-Clock Time 176 viii Contents 8.8 The mlock Family: Locking Physical Memory 177 8.9 mprotect: Setting Memory Permissions 179 8.10 nanosleep: High-Precision Sleeping 181 8.11 readlink: Reading Symbolic Links 182 8.12 sendfile: Fast Data Transfers 183 8.13 setitimer. Setting Interval Timers 185 8.14 sysinfo: Obtaining System Statistics 186 8.15 uname 187 9 Inline Assembly Code 189 9.1 When to Use Assembly Code 190 9.2 Simple Inline Assembly 191 9.3 Extended Assembly Syntax 192 9.4 Example 194 9.5 Optimization Issues 196 9.6 Maintenance and Portability Issues 196 10 Security 197 10.1 Users and Groups 198 10.2 Process User IDs and Process Group IDs 199 10.3 File System Permissions 200 10.4 Real and Effective IDs 205 10.5 Authenticating Users 208 10.6 More Security Holes 211 11 A Sample GNU/Linux Application 219 11.1 Overview 219 11.2 Implementation 221 11.3 Modules 239 11.4 Using the Server 252 11.5 Finishing Up 255 Contents ix III Appendixes 257 A Other Development Tools 259 A. 1 Static Program Analysis 259 A. 2 Finding Dynamic Memory Errors 261 A.3 Profiling 269 B Low-Level I/O 281 B.l Reading and Writing Data 282 B.2 stat 291 B.3 Vector Reads and Writes 293 B.4 Relation to Standard C Library I/O Functions 295 B.5 Other File Operations 296 B.6 Reading Directory Contents 296 C Table of Signals 301 D Online Resources 303 D. 1 General Information 303 D.2 Information About GNU/Linux Software 304 D.3 Other Sites 304 E Open Publication License Version 1.0 305 I. Requirement on Both Unmodified and Modified Versions 305 II. Copyright 306 III. Scope of License 306 IV Requirements on Modified Works 306 V Good-Practice Recommendations 306 VI. License Options 307 Open Publication Policy Appendix 307 Contents GNU General Public License 309 Preamble 309 Terms and Conditions for Copying, Distribution and Modification 310 End of Terms and Conditions 315 How to Apply These Terms to Your New Programs 315 Index 317 Table of Program Listings 1.1 main.c (C source file), 6 1.2 reciprocal. cpp (C++ source file), 6 1.3 reciprocal. hpp (header file), 7 2.1 arglist.c (argc and argv parameters), 18 2.2 getopt_long.c (getopt_long function), 21 2.3 print_env.c (printing execution environment), 26 2.4 client. c (network client program), 26 2.5 temp_file.c (mkstemp function), 28 2.6 readfile.c (resource allocation during error checking), 35 2.7 test.c (library contents), 37 2.8 app.c (program with library functions), 37 2.9 tifftest.c (libtiff library), 40 3.1 print-pid.c (printing process IDs), 46 3.2 system. c (system function), 48 3.3 fork.c (fork function), 49 3.4 fork-exec. c (fork and exec functions), 51 3.5 sigusrl.c (signal handlers), 54 3.6 zombie.c (zombie processes), 58 3.7 sigchld.c (cleaning up child processes), 60 4.1 thread-create. c (creating threads), 63 4.2 thread-create2 (creating two threads), 64 4.3 thread-create2.c (revised main function), 65 4.4 primes. c (prime number computation in a thread), 67 4.5 detached.c (creating detached threads), 69 4.6 critical-section. c (critical sections), 71 4.7 tsd.c (thread-specific data), 73 4.8 cleanup.c (cleanup handlers), 75 4.9 cxx-exit.cpp (C++ thread cleanup), 76 4.10 job-queuel.c (thread race conditions), 78 4.11 job-queue2.c (mutexes), 80 4.12 job-queue3.c (semaphores), 84 4.13 spin-condvar.c (condition variables), 87 Program Listings xiii 4.14 condvar.c (condition variables), 90 4.15 thread-pid (printing thread process IDs), 92 5.1 shm.c (shared memory), 99 5.2 sem_all_deall.c (semaphore allocation and deallocation), 102 5.3 sem_init.c (semaphore initialization), 102 5.4 sem_pv.c (semaphore wait and post operations), 104 5.5 mmap-write.c (mapped memory), 106 5.6 mmap-read.c (mapped memory), 107 5.7 pipe.c (parent-child process communication), 111 5.8 dup2.c (output redirection), 113 5.9 popen.c (popen command), 114 5.10 socket-server.c (local sockets), 120 5.11 socket-client. c (local sockets), 121 5.12 socket-inet.c (Internet-domain sockets), 124 6.1 random_number.c (random number generation), 138 6.2 cdrom-eject.c (ioctl example), 144 7.1 clock-speed.c (cpu clock speed from /proc/cpuinfo), 149 7.2 get-pid.c (process ID from /proc/self), 151 7.3 print-arg-list.c (printing process argument lists), 153 7.4 print-environment. c (process environment), 154 7.5 get-exe-path.c (program executable path), 155 7.6 open-and-spin.c (opening files), 157 7.7 print-uptime.c (system uptime and idle time), 165 8.1 check-access. c (file access permissions), 170 8.2 lock-file. c (write lo...
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