Beginning Linux Programming

Neil Matthew has been interested in and has programmed computers since 1974. A mathematics graduate from the University of Nottingham, Neil is just plain keen on programming languages and likes to explore new ways of solving computing problems. He’s written systems to program in BCPL, FP (Functional Programming), Lisp, Prolog, and a structured BASIC. He even wrote a 6502 microprocessor emulator to run BBC microcomputer programs on UNIX systems. In terms of UNIX experience, Neil has used almost every flavor since the late 1970s, including BSD UNIX, AT&T System V, Sun Solaris, IBM AIX, many others, and of course Linux. He can claim to have been using Linux since August 1993 when he acquired a floppy disk distribution of Soft Landing (SLS) from Canada, with kernel version 0.99.11. He’s used Linux-based computers for hacking C, C++, Icon, Prolog, Tcl, and Java at home and at work. All of Neil’s "home" projects are developed using Linux. He says Linux is much easier because it supports quite a lot of features from other systems, so that both BSD- and System V-targeted programs will generally compile with little or no change. Neil is currently working as an Enterprise Architect specializing in IT strategy at Celesio AG. He has a background in technical consultancy, software development techniques, and quality assurance. Neil has also programmed in C and C++ for real-time embedded systems. Rick Stones started programming at school (more years ago than he cares to remember) on a 6502-powered BBC micro, which, with the help of a few spare parts, continued to function for the next 15 years. He graduated from Nottingham University with a degree in Electronic Engineering, but decided software was more fun. Over the years he has worked for a variety of companies, from the very small with just a dozen employees, to the very large, including the IT services giant EDS. Along the way he has worked on a range of projects, from real-time communications to accounting systems, to very large help desk systems. He is currently working as an IT architect, acting as a technical authority on various major projects for a large pan-European company. A bit of a programming linguist, he has programmed in various assemblers, a rather neat proprietary telecommunications language called SL-1, some FORTRAN, Pascal, Perl, SQL, and smidgeons of Python and C++, as well as C. (Under duress he even admits that he was once reasonably proficient in Visual Basic, but tries not to advertise this aberration.)

Acknowledgements x

Foreword xxiii

Introduction xxv

Chapter 1: Getting Started 1

An Introduction to UNIX, Linux, and GNU 1

What Is UNIX? 1

What Is Linux? 3

The GNU Project and the Free Software Foundation 3

Linux Distributions 4

Programming Linux 4

Linux Programs 5

Text Editors 6

The C Compiler 7

Development System Roadmap 8

Getting Help 14

Summary 16

Chapter 2: Shell Programming 17

Why Program with a Shell? 18

A Bit of Philosophy 18

What Is a Shell? 19

Pipes and Redirection 21

Redirecting Output 21

Redirecting Input 22

Pipes 22

The Shell as a Programming Language 23

Interactive Programs 23

Creating a Script 24

Making a Script Executable 25

Shell Syntax 27

Variables 27

Conditions 31

Control Structures 34

Functions 46

Commands 49

Command Execution 68

Here Documents 73

Debugging Scripts 74

Going Graphical — The dialog Utility 75

Putting It All Together 81

Requirements 82

Design 82

Summary 91

Chapter 3: Working with Files 93

Linux File Structure 94

Directories 94

Files and Devices 95

System Calls and Device Drivers 96

Library Functions 97

Low-Level File Access 98

write 98

read 99

open 100

Initial Permissions 101

Other System Calls for Managing Files 106

The Standard I/O Library 109

fopen 110

fread 110

fwrite 111

fclose 111

fflush 111

fseek 112

fgetc, getc, and getchar 112

fputc, putc, and putchar 112

fgets and gets 113

Formatted Input and Output 113

printf, fprintf, and sprintf 113

scanf, fscanf, and sscanf 115

Other Stream Functions 117

Stream Errors 119

Streams and File Descriptors 119

File and Directory Maintenance 120

chmod 120

chown 120

unlink, link, and symlink 121

mkdir and rmdir 121

chdir and getcwd 122

Scanning Directories 122

opendir 123

readdir 123

telldir 123

seekdir 124

closedir 124

Errors 127

strerror 127

perror 127

The /proc File System 128

Advanced Topics: fcntl and mmap 132

fcntl 132

mmap 133

Summary 135

Chapter 4: The Linux Environment 137

Program Arguments 137

getopt 140

getopt_long 142

Environment Variables 144

Use of Environment Variables 146

The environ Variable 147

Time and Date 148

Temporary Files 156

User Information 158

Host Information 161

Logging 163

Resources and Limits 167

Summary 173

Chapter 5: Terminals 175

Reading from and Writing to the Terminal 175

Talking to the Terminal 180

The Terminal Driver and the General Terminal Interface 182

Overview 183

Hardware Model 183

The termios Structure 184

Input Modes 186

Output Modes 186

Control Modes 187

Local Modes 188

Special Control Characters 188

Terminal Speed 192

Additional Functions 192

Terminal Output 196

Terminal Type 197

Identify Your Terminal Type 197

Using terminfo Capabilities 200

Detecting Keystrokes 205

Virtual Consoles 207

Pseudo-Terminals 208

Summary 209

Chapter 6: Managing Text-Based Screens with curses 211

Compiling with curses 212

Curses Terminology and Concepts 213

The Screen 216

Output to the Screen 216

Reading from the Screen 217

Clearing the Screen 218

Moving the Cursor 218

Character Attributes 218

The Keyboard 221

Keyboard Modes 221

Keyboard Input 222

Windows 224

The WINDOW Structure 224

Generalized Functions 225

Moving and Updating a Window 225

Optimizing Screen Refreshes 229

Subwindows 230

The Keypad 232

Using Color 235

Redefining Colors 238

Pads 238

The CD Collection Application 240

Starting a New CD Collection Application 240

Looking at main 243

Building the Menu 243

Database File Manipulation 245

Querying the CD Database 250

Summary 254

Chapter 7: Data Management 255

Managing Memory 255

Simple Memory Allocation 256

Allocating Lots of Memory 257

Abusing Memory 260

The Null Pointer 261

Freeing Memory 262

Other Memory Allocation Functions 264

File Locking 264

Creating Lock Files 265

Locking Regions 268

Use of read and write with Locking 271

Competing Locks 276

Other Lock Commands 280

Deadlocks 280

Databases 281

The dbm Database 281

The dbm Routines 283

dbm Access Functions 283

Additional dbm Functions 287

The CD Application 289

Updating the Design 289

The CD Database Application Using dbm 290

Summary 309

Chapter 8: MySQL 311

Installation 312

MySQL Packages 312

Post-Install Configuration 314

Post-Installation Troubleshooting 319

MySQL Administration 320

Commands 320

Creating Users and Giving Them Permissions 325

Passwords 327

Creating a Database 328

Data Types 329

Creating a Table 330

Graphical Tools 333

Accessing MySQL Data from C 335

Connection Routines 337

Error Handling 341

Executing SQL Statements 342

Miscellaneous Functions 357

The CD Database Application 358

Creating the Tables 359

Adding Some Data 362

Accessing the Application Data from C 364

Summary 375

Chapter 9: Development Tools 377

Problems of Multiple Source Files 377

The make Command and Makefiles 378

The Syntax of Makefiles 378

Options and Parameters to make 379

Comments in a Makefile 382

Macros in a Makefile 382

Multiple Targets 384

Built-in Rules 387

Suffix and Pattern Rules 388

Managing Libraries with make 389

Advanced Topic: Makefiles and Subdirectories 391

GNU make and gcc 391

Source Code Control 392

RCS 393

SCCS 399

Comparing RCS and SCCS 399

CVS 400

CVS Front Ends 404

Subversion 405

Writing a Manual Page 406

Distributing Software 409

The patch Program 410

Other Distribution Utilities 411

RPM Packages 413

Working with RPM Package Files 414

Installing RPM Packages 415

Building RPM Packages 415

Other Package Formats 424

Development Environments 424

KDevelop 425

Other Environments 425

Summary 427

Chapter 10: Debugging 429

Types of Errors 429

General Debugging Techniques 430

A Program with Bugs 430

Code Inspection 433

Instrumentation 434

Controlled Execution 436

Debugging with gdb 437

Starting gdb 437

Running a Program 438

Stack Trace 438

Examining Variables 439

Listing the Program 440

Setting Breakpoints 441

Patching with the Debugger 444

Learning More about gdb 445

More Debugging Tools 445

Lint: Removing the Fluff from Your Programs 446

Function Call Tools 449

Execution Profiling with prof/gprof 451

Assertions 452

Memory Debugging 453

ElectricFence 454

valgrind 455

Summary 459

Chapter 11: Processes and Signals 461

What Is a Process? 461

Process Structure 462

The Process Table 463

Viewing Processes 463

System Processes 464

Process Scheduling 467

Starting New Processes 468

Waiting for a Process 475

Zombie Processes 477

Input and Output Redirection 479

Threads 480

Signals 481

Sending Signals 484

Signal Sets 489

Summary 493

Chapter 12: POSIX Threads 495

What Is a Thread? 495

Advantages and Drawbacks of Threads 496

A First Threads Program 497

Simultaneous Execution 501

Synchronization 503

Synchronization with Semaphores 503

Synchronization with Mutexes 508

Thread Attributes 512

Canceling a Thread 517

Threads in Abundance 520

Summary 524

Chapter 13: Inter-Process Communication: Pipes 525

What Is a Pipe? 525

Process Pipes 526

Sending Output to popen 528

Passing More Data 529

How popen Is Implemented 530

The Pipe Call 531

Parent and Child Processes 535

Reading Closed Pipes 536

Pipes Used as Standard Input and Output 537

Named Pipes: FIFOs 540

Accessing a FIFO 542

Advanced Topic: Client/Server Using FIFOs 549

The CD Database Application 553

Aims 554

Implementation 555

Client Interface Functions 558

The Server Interface, server.c 565

The Pipe 569

Application Summary 574

Summary 575

Chapter 14: Semaphores, Shared Memory, and Message Queues 577

Semaphores 577

Semaphore Definition 579

A Theoretical Example 579

Linux Semaphore Facilities 580

Using Semaphores 582

Shared Memory 586

shmget 588

shmat 588

shmdt 589

shmctl 589

Message Queues 594

msgget 594

msgsnd 595

msgrcv 595

msgctl 596

The CD Database Application 599

Revising the Server Functions 600

Revising the Client Functions 602

IPC Status Commands 604

Displaying Semaphore Status 604

Displaying Shared Memory Status 604

Displaying Message Queue Status 605

Summary 605

Chapter 15: Sockets 607

What Is a Socket? 608

Socket Connections 608

Socket Attributes 612

Creating a Socket 614

Socket Addresses 615

Naming a Socket 616

Creating a Socket Queue 617

Accepting Connections 617

Requesting Connections 618

Closing a Socket 619

Socket Communications 619

Host and Network Byte Ordering 622

Network Information 624

The Internet Daemon (xinetd/inetd) 629

Socket Options 631

Multiple Clients 632

select 635

Multiple Clients 638

Datagrams 642

Summary 644

Chapter 16: Programming GNOME Using GTK+ 645

Introducing X 645

X Server 646

X Client 646

X Protocol 646

Xlib 647

Toolkits 647

Window Managers 647

Other Ways to Create a GUI — Platform-Independent Windowing APIs 648

Introducing GTK+ 648

GLib Type System 649

GTK+ Object System 650

Introducing GNOME 651

Installing the GNOME/GTK+ Development Libraries 652

Events, Signals, and Callbacks 655

Packing Box Widgets 658

GTK+ Widgets 661

GtkWindow 662

GtkEntry 663

GtkSpinButton 666

GtkButton 668

GtkTreeView 672

GNOME Widgets 676

GNOME Menus 677

Dialogs 682

GtkDialog 682

Modal Dialog Box 684

Nonmodal Dialogs 685

GtkMessageDialog 686

CD Database Application 687

Summary 699

Chapter 17: Programming KDE Using Qt 701

Introducing KDE and Qt 701

Installing Qt 702

Signals and Slots 705

Qt Widgets 712

QLineEdit 712

Qt Buttons 716

QComboBox 721

QListView 724

Dialogs 727

QDialog 728

QMessageBox 730

QInputDialog 731

Using qmake to Simplify Writing Makefiles 733

Menus and Toolbars with KDE 733

CD Database Application Using KDE/Qt 738

MainWindow 738

AddCdDialog 742

LogonDialog 743

main.cpp 745

Summary 746

Chapter 18: Standards for Linux 747

The C Programming Language 748

A Brief History Lesson 748

The GNU Compiler Collection 749

gcc Options 749

Interfaces and the Linux Standards Base 751

LSB Standard Libraries 752

LSB Users and Groups 754

LSB System Initialization 754

The Filesystem Hierarchy Standard 755

Further Reading about Standards 758

Summary 759

Index 761