Advanced Programming in the UNIX Environment

Foreword to the Second Edition xix

Preface xxi

Preface to the Second Edition xxv

Preface to the First Edition xxix



Chapter 1: UNIX System Overview 1

1.1 Introduction 1

1.2 UNIX Architecture 1

1.3 Logging In 2

1.4 Files and Directories 4

1.5 Input and Output 8

1.6 Programs and Processes 10

1.7 Error Handling 14

1.8 User Identification 16

1.9 Signals 18

1.10 Time Values 20

1.11 System Calls and Librar y Functions 21

1.12 Summary 23



Chapter 2: UNIX Standardization and Implementations 25

2.1 Introduction 25

2.2 UNIX Standardization 25

2.3 UNIX System Implementations 33

2.4 Relationship of Standards and Implementations 36

2.5 Limits 36

2.6 Options 53

2.7 Feature Test Macros 57

2.8 Primitive System Data Types 58

2.9 Differences Between Standards 58

2.10 Summary 60



Chapter 3: File I/O 61

3.1 Introduction 61

3.2 File Descr iptors 61

3.3 open and openat Functions 62

3.4 creat Function 66

3.5 close Function 66

3.6 lseek Function 66

3.7 read Function 71

3.8 write Function 72

3.9 I/O Efficiency 72

3.10 File Shar ing 74

3.11 Atomic Operations 77

3.12 dup and dup2 Functions 79

3.13 sync, fsync, and fdatasync Functions 81

3.14 fcntl Function 82

3.15 ioctl Function 87

3.16 /dev/fd 88

3.17 Summary 90



Chapter 4: Files and Directories 93

4.1 Introduction 93

4.2 stat, fstat, fstatat, and lstat Functions 93

4.3 File Types 95

4.4 Set-User-ID and Set-Group-ID 98

4.5 File Access Per missions 99

4.6 Ownership of New Files and Directories 101

4.7 access and faccessat Functions 102

4.8 umask Function 104

4.9 chmod, fchmod, and fchmodat Functions 106

4.10 Sticky Bit 108

4.11 chown, fchown, fchownat, and lchown Functions 109

4.12 File Size 111

4.13 File Tr uncation 112

4.14 File Systems 113

4.15 link, linkat, unlink, unlinkat, and remove Functions 116

4.16 rename and renameat Functions 119

4.17 Symbolic Links 120

4.18 Creating and Reading Symbolic Links 123

4.19 File Times 124

4.20 futimens, utimensat, and utimes Functions 126

4.21 mkdir, mkdirat, and rmdir Functions 129

4.22 Reading Director ies 130

4.23 chdir, fchdir, and getcwd Functions 135

4.24 Device Special Files 137

4.25 Summary of File Access Per mission Bits 140

4.26 Summary 140



Chapter 5: Standard I/O Library 143

5.1 Introduction 143

5.2 Streams and FILE Objects 143

5.3 Standard Input, Standard Output, and Standard Error 145

5.4 Buffer ing 145

5.5 Opening a Stream 148

5.6 Reading and Writing a Stream 150

5.7 Line-at-a-Time I/O 152

5.8 Standard I/O Efficiency 153

5.9 Binary I/O 156

5.10 Positioning a Stream 157

5.11 For matted I/O 159

5.12 Implementation Details 164

5.13 Temporar y Files 167

5.14 Memory Streams 171

5.15 Alternatives to Standard I/O 174

5.16 Summary 175



Chapter 6: System Data Files and Information 177

6.1 Introduction 177

6.2 Password File 177

6.3 Shadow Passwords 181

6.4 Group File 182

6.5 Supplementary Group IDs 183

6.6 Implementation Differences 184

6.7 Other Data Files 185

6.8 Login Accounting 186

6.9 System Identification 187

6.10 Time and Date Routines 189

6.11 Summary 196



Chapter 7: Process Environment 197

7.1 Introduction 197

7.2 main Function 197

7.3 Process Termination 198

7.4 Command-Line Arguments 203

7.5 Environment List 203

7.6 Memory Lay out of a C Program 204

7.7 Shared Librar ies 206

7.8 Memory Allocation 207

7.9 Environment Var iables 210

7.10 setjmp and longjmp Functions 213

7.11 getrlimit and setrlimit Functions 220

7.12 Summary 225



Chapter 8: Process Control 227

8.1 Introduction 227

8.2 Process Identifiers 227

8.3 fork Function 229

8.4 vfork Function 234

8.5 exit Functions 236

8.6 wait and waitpid Functions 238

8.7 waitid Function 244

8.8 wait3 and wait4 Functions 245

8.9 Race Conditions 245

8.10 exec Functions 249

8.11 Changing User IDs and Group IDs 255

8.12 Interpreter Files 260

8.13 system Function 264

8.14 Process Accounting 269

8.15 User Identification 275

8.16 Process Scheduling 276

8.17 Process Times 280

8.18 Summary 282



Chapter 9: Process Relationships 285

9.1 Introduction 285

9.2 Ter minal Logins 285

9.3 Networ k Logins 290

9.4 Process Groups 293

9.5 Sessions 295

9.6 Controlling Terminal 296

9.7 tcgetpgrp, tcsetpgrp, and tcgetsid Functions 298

9.8 Job Control 299

9.9 Shell Execution of Programs 303

9.10 Orphaned Process Groups 307

9.11 FreeBSD Implementation 310

9.12 Summary 312



Chapter 10: Signals 313

10.1 Introduction 313

10.2 Signal Concepts 313

10.3 signal Function 323

10.4 Unreliable Signals 326

10.5 Interrupted System Calls 327

10.6 Reentrant Functions 330

10.7 SIGCLD Semantics 332

10.8 Reliable-Signal Ter minology and Semantics 335

10.9 kill and raise Functions 336

10.10 alarm and pause Functions 338

10.11 Signal Sets 344

10.12 sigprocmask Function 346

10.13 sigpending Function 347

10.14 sigaction Function 349

10.15 sigsetjmp and siglongjmp Functions 355

10.16 sigsuspend Function 359

10.17 abort Function 365

10.18 system Function 367

10.19 sleep, nanosleep, and clock_nanosleep Functions 373

10.20 sigqueue Function 376

10.21 Job-Control Signals 377

10.22 Signal Names and Numbers 379

10.23 Summary 381



Chapter 11: Threads 383

11.1 Introduction 383

11.2 Thread Concepts 383

11.3 Thread Identification 384

11.4 Thread Creation 385

11.5 Thread Termination 388

11.6 Thread Synchronization 397

11.7 Summary 422



Chapter 12: Thread Control 425

12.1 Introduction 425

12.2 Thread Limits 425

12.3 Thread Attr ibutes 426

12.4 Synchronization Attr ibutes 430

12.5 Reentrancy 442

12.6 Thread-Specific Data 446

12.7 Cancel Options 451

12.8 Threads and Signals 453

12.9 Threads and fork 457

12.10 Threads and I/O 461

12.11 Summary 462



Chapter 13: Daemon Processes 463

13.1 Introduction 463

13.2 Daemon Character istics 463

13.3 Coding Rules 466

13.4 Error Logging 469

13.5 Single-Instance Daemons 473

13.6 Daemon Conventions 474

13.7 Client-Server Model 479

13.8 Summary 480



Chapter 14: Advanced I/O 481

14.1 Introduction 481

14.2 Nonblocking I/O 481

14.3 Record Locking 485

14.4 I/O Multiplexing 500

14.5 Asynchronous I/O 509

14.6 readv and writev Functions 521

14.7 readn and writen Functions 523

14.8 Memory-Mapped I/O 525

14.9 Summary 531



Chapter 15: Interprocess Communication 533

15.1 Introduction 533

15.2 Pipes 534

15.3 popen and pclose Functions 541

15.4 Coprocesses 548

15.5 FIFOs 552

15.6 XSI IPC 556

15.7 Message Queues 561

15.8 Semaphores 565

15.9 Shared Memor y 571

15.10 POSIX Semaphores 579

15.11 Client-Server Proper ties 585

15.12 Summary 587



Chapter 16: Network IPC: Sockets 589

16.1 Introduction 589

16.2 Socket Descr iptors 590

16.3 Addressing 593

16.4 Connection Establishment 605

16.5 Data Tr ansfer 610

16.6 Socket Options 623

16.7 Out-of-Band Data 626

16.8 Nonblocking and Asynchronous I/O 627

16.9 Summary 628



Chapter 17: Advanced IPC 629

17.1 Introduction 629

17.2 UNIX Domain Sockets 629

17.3 Unique Connections 635

17.4 Passing File Descriptors 642

17.5 An Open Server, Version 1 653

17.6 An Open Server, Version 2 659

17.7 Summary 669



Chapter 18: Terminal I/O 671

18.1 Introduction 671

18.2 Over view 671

18.3 Special Input Characters 678

18.4 Getting and Setting Ter minal Attr ibutes 683

18.5 Ter minal Option Flags 683

18.6 stty Command 691

18.7 Baud Rate Functions 692

18.8 Line Control Functions 693

18.9 Ter minal Identification 694

18.10 Canonical Mode 700

18.11 Noncanonical Mode 703

18.12 Ter minal Window Size 710

18.13 termcap, terminfo, and curses 712

18.14 Summary 713



Chapter 19: Pseudo Terminals 715

19.1 Introduction 715

19.2 Over view 715

19.3 Opening Pseudo-Ter minal Devices 722

19.4 pty_fork Function 726

19.5 pty Program 729

19.6 Using the pty Program 733

19.7 Advanced Features 740

19.8 Summary 741



Chapter 20: A Database Library 743

20.1 Introduction 743

20.2 History 743

20.3 The Librar y 744

20.4 Implementation Over view 746

20.5 Centralized or Decentralized? 750

20.6 Concurrency 752

20.7 Building the Librar y 753

20.8 Source Code 753

20.9 Perfor mance 781

20.10 Summary 786



Chapter 21: Communicating with a Network Printer 789

21.1 Introduction 789

21.2 The Inter net Pr inting Protocol 789

21.3 The Hyper text Transfer Protocol 792

21.4 Printer Spooling 793

21.5 Source Code 795

21.6 Summary 843



Appendix A: Function Prototypes 845



Appendix B: Miscellaneous Source Code 895

B.1 Our Header File 895

B.2 Standard Error Routines 898



Appendix C: Solutions to Selected Exercises 905





Bibliography 947

Index 955