Linux Application Development by Example

Arnold Robbins is a professional software engineer and technical author. He has been working with Unix systems of various sorts, GNU/Linux systems, C, C++, and all the other major Unix tools since 1980. As a long-time volunteer for the GNU project, he has been the maintainer of gawk (GNU Awk) for many years. In 2024, he was awarded the USENIX Lifetime Achievement Award ("The Flame") for his work on GNU Awk and for his numerous books on topics related to Unix and Linux.

Praise for the Second Edition"This may be the most clearly written narrative-style coverage of the topic that I have encountered and one of the most complete that is not solely a reference work."[The book] has forced me to think differently about some of these topics and how they build on one another. It's almost like when I studied LISP way back when and it turned all my thinking about programming on its head. Thank you! It is a privilege to review this."This is one of the better-crafted tech books I've reviewed across two decades. The exercises consistently help the reader focus on specific things in the text and gently struggle and learn concepts that might otherwise slip through the cracks. I failed to find any exercise that I would delete and can't think of any I would add."--Matthew Helmke, Linux author and consultantPraise for the First Edition"This is an excellent introduction to Linux programming. The topics are well chosen and lucidly presented. I learned things myself, especially about internationalization, and I've been at this for quite a while."--Chet Ramey, coauthor and maintainer of the Bash shell"This is a good introduction to Linux programming. Arnold's technique of showing how experienced programmers use the Linux programming interfaces is a nice touch, much more useful than the canned programming examples found in most books."--Ulrich Drepper, project lead, GNU C library"A gentle yet thorough introduction to the art of UNIX system programming, Linux Programming by Example uses code from a wide range of familiar programs to illustrate each concept it teaches. Readers will enjoy an interesting mix of in-depth API descriptions and portability guidelines, and will come away well prepared to begin reading and writing systems applications. Heartily recommended."--Jim Meyering, coauthor and maintainer of the GNU Core Utility Programs

• Foreword xvPreface xviiPart I: Files and Users 1Chapter 1: Introduction 31.1 The Linux/Unix File Model 31.2 The Linux/Unix Process Model 71.3 Standard C versus Original C 91.4 Why GNU Programs Are Better 131.5 Portability Revisited 171.6 Some Words about Coding Style 181.7 Artificial Intelligence Isn't Intelligent 191.8 Suggested Reading 191.9 Summary 20Exercises 21Chapter 2: Arguments, Options, and the Environment 232.1 Option and Argument Conventions 232.2 Basic Command-Line Processing 262.3 Option Parsing: getopt() and getopt_long() 282.4 The Environment 372.5 Summary 49Exercises 49Chapter 3: User-Level Memory Management 513.1 Linux/Unix Address Space 513.2 Memory Allocation 553.3 Summary 76Exercises 77Chapter 4: Files and File I/O 794.1 Introducing the Linux/Unix I/O Model 794.2 Presenting a Basic Program Structure 794.3 Determining What Went Wrong 814.4 Doing Input and Output 874.5 Random Access: Moving Around within a File 964.6 Creating Files 1014.7 Forcing Data to Disk 1064.8 Setting File Length 1074.9 Summary 108Exercises 109Chapter 5: Directories and File Metadata 1115.1 Considering Directory Contents 1115.2 Creating and Removing Directories 1215.3 Reading Directories 1235.4 Obtaining Information about Files 1305.5 Avoiding Race Conditions: openat() and Friends 1445.6 Changing Ownership, Permission, and Modification Times 1455.7 Summary 151Exercises 153Chapter 6: General Library Interfaces--Part 1 1556.1 Times and Dates 1556.2 Sorting and Searching Functions 1716.3 User and Group Names 1906.4 Terminals: isatty() 1966.5 Suggested Reading 1966.6 Summary 197Exercises 198Chapter 7: Putting It All Together: ls 2017.1 V7 ls Options 2017.2 V7 ls Code 2027.3 Summary 218Exercises 218Chapter 8: Filesystems and Directory Walks 2218.1 Mounting and Unmounting Filesystems 2218.2 Files for Filesystem Administration 2288.3 Retrieving Per-Filesystem Information 2348.4 Moving Around in the File Hierarchy 2478.5 Processing a File Hierarchy: GNU du 2618.6 Changing the Root Directory: chroot() 2698.7 Summary 270Exercises 271Part II: Processes, Networking, and Internationalization 273Chapter 9: Process Management and Pipes 2759.1 Process Creation and Management 2759.2 Process Groups 3009.3 Basic Interprocess Communication: Pipes and FIFOs 3029.4 File Descriptor Management 3079.5 Example: Two-Way Pipes in gawk 3239.6 Suggested Reading 3279.7 Summary 328Exercises 330Chapter 10: Signals 33310.1 Introduction 33310.2 Signal Actions 33310.3 Standard C Signals: signal() and raise() 33410.4 Signal Handlers in Action 33710.5 The System V Release 3 Signal APIs: sigset() et al. 34910.6 POSIX Signals 35010.7 Signals for Interprocess Communication 36010.8 Important Special-Purpose Signals 36310.9 Signals across fork() and exec() 37810.10 Summary 379Exercises 381Chapter 11: Permissions and User and Group ID Numbers 38311.1 Checking Permissions 38311.2 Retrieving User and Group IDs 38511.3 Checking as the Real User: access() 38811.4 Setting Extra Permission Bits for Directories 39111.5 Setting Real and Effective IDs 39311.6 Working with All Three IDs: getresuid() and setresuid() (Linux) 39811.7 Crossing a Security Minefield: Setuid root 39911.8 Suggested Reading 40011.9 Summary 401Exercises 403Chapter 12: Resource Limits 40512.1 Introduction 40512.2 System Limits: sysconf(), pathconf(), and fpathconf() 40512.3 Getting Configuration String Variables: confstr() 41112.4 Basic Process Limits: ulimit() 41312.5 Hard and Soft Limits: getrlimit() and setrlimit() 41412.6 Summary 417Exercises 418Chapter 13: General Library Interfaces--Part 2 41913.1 Assertion Statements: assert() 41913.2 Low-Level Memory: The memXXX() Functions 42313.3 Temporary Files 42613.4 Committing Suicide: abort() 43413.5 Nonlocal Gotos 43513.6 Pseudorandom Numbers 44213.7 Metacharacter Expansions 45013.8 Regular Expressions 45913.9 Suggested Reading 46713.10 Summary 468Exercises 469Chapter 14: Sockets and Basic Networking 47314.1 Introduction, with a Little Bit of History 47314.2 Networking Technologies 47414.3 Internet Building Blocks 47414.4 Networking and Client/Server 47714.5 Basic Structure of a Server Program 47814.6 Basic Structure of a Client Program 48814.7 Specialized Send and Receive Functions 49214.8 Handling Multiple Open Connections: select() 49414.9 pselect(): A Smarter Version of select() 50114.10 Unix-Domain Sockets 50214.11 Suggested Reading 50214.12 Summary 503Exercises 504Chapter 15: Internationalization and Localization 50715.1 Introduction 50715.2 Locales and the C Library 50815.3 Dynamic Translation of Program Messages 52615.4 Can You Spell That for Me, Please? 54015.5 Suggested Reading 55315.6 Summary 553Exercises 555Chapter 16: Extended Interfaces 55716.1 Allocating Aligned Memory: posix_memalign() and memalign() 55716.2 Locking Files 55816.3 More Precise Times 56716.4 Advanced Searching with Binary Trees 57516.5 Summary 586Exercises 587Part III: Debugging and Final Project 589Chapter 17: Debugging 59117.1 First Things First 59117.2 Compilation for Debugging 59217.3 GDB Basics 59317.4 Programming for Debugging 60617.5 Debugging Tools I: A Modern lint 63217.6 Debugging Tools II: Memory Allocation Debuggers 63317.7 Asking for Help 65017.8 Software Testing 65117.9 Debugging Rules 65317.10 Suggested Reading 65517.11 Summary 656Exercises 657Chapter 18: A Project That Ties Everything Together 65918.1 Project Description 65918.2 Suggested Reading 661Part IV: Appendices 663Appendix A: Teach Yourself Programming in Ten Years 665Appendix B: Caldera Ancient UNIX License 671Appendix C: GNU General Public License 673Appendix D: License for the One True Awk 685Appendix E: License for 4.4 BSD Code 687Index 689