Linux Programming Unleashed.pdf

Introduction

Linux has always provided a rich programming environment, and it has only grown rich-

er. Two new compilers, egcs and pgcs , joined the GNU project’s gcc , the original Linux

compiler. In fact, as this book went to press, the Free Software Foundation, custodians of

the GNU project, announced that gcc would be maintained by the creators and maintain-

ers of egcs . A huge variety of editors stand alongside the spartan and much-maligned vi

and emacs’ marvelous complexity. Driven largely by the Linux kernel, GNU’s C library

has evolved so dramatically that a new version, glibc (also known as libc6) has emerged

as the standard C library. Linux hackers have honed the GNU project’s always service-

able development suite into powerful tools. New widget sets have taken their place

beside the old UNIX standbys. Lesstif is a free, source-compatible implementation of

Motif 1.2; KDE, the K Desktop Environment based on the Qt class libraries from

TrollTech, answers the desktop challenge posed by the X Consortium’s CDE (Common

Desktop Environment).

What This Book Will Do for You

In this book, we propose to show you how to program in, on, and for Linux. We’ll

focus almost exclusively on the C language because C is still Linux’s lingua franca.

After introducing you to some essential development tools, we dive right in to

system programming, followed by a section on interprocess communication and network

programming.

After a section devoted to programming Linux’s user interface with both text-based and

graphical tools (the X Window system), a section on specialized topics, including shell

programming, security considerations, and using the GNU project’s gdb debugger,

rounds out the technical discussion. We close the book with three chapters on a topic

normally disregarded in programming books: delivering your application to users. These

final chapters show you how to use package management tools such as RPM, how to

create useful documentation, and discuss licensing issues and options. If we’ve done our

job correctly, you should be well prepared to participate in the great sociological and

technological phenomenon called “Linux.”

Intended Audience

Programmers familiar with other operating systems but new to Linux get a solid intro-

duction to programming under Linux. We cover both the tools you will use and the

environment in which you will be working.

Linux Programming

U NLEASHED

Experienced UNIX programmers will find Linux’s programming idioms very familiar.

What we hope to accomplish for this group is to highlight the differences you will

encounter. Maximum portability will be an important topic because Linux runs on an

ever-growing variety of platforms: Intel i386, Sun Sparcs, Digital Alphas, MIPS proces-

sors, Power PCs, and Motorola 68000-based Macintosh computers.

Intermediate C programmers will also gain a lot from this book. In general, program-

ming Linux is similar to programming any other UNIX-like system, so we start you on

the path toward becoming an effective UNIX programmer and introduce you to the pecu-

liarities of Linux/UNIX hacking.

Linux Programming Unleashed ,

Chapter by Chapter

This is not a C tutorial, but you will get a very quick refresher. You will need to be able

to read and understand C code and understand common C idioms. Our selection of tools

rarely strays from the toolbox available from the GNU project. The reason for this is

simple: GNU software is standard equipment in every Linux distribution.

The first seven chapters cover setting up a development system and using the standard

Linux development tools:

• gcc

• make

• autoconf

• diff

• patch

• RCS

• emacs

The next section introduces system programming topics. If you are a little rusty on the

standard C library, Chapter 9 will clear the cobwebs. Chapter 10 covers Linux’s file

manipulation routines. Chapter 11 answers the question, “What is a process?” and shows

you the system calls associated with processes and job control. We teach you how to get

system information in Chapter 12, and then get on our editorial soapbox in Chapter 13

and lecture you about why error-checking is A Good Thing. Of course, we’ll show you

how to do it, too. Chapter 14 is devoted to the vagaries of memory management under

Linux.

I NTRODUCTION

We spend four chapters on various approaches to interprocess communication using

pipes, message queues, shared memory, and semaphores. Four more chapters show you

how to write programs based on the TCP/IP network protocol. After a general introduc-

tion to creating and using programming libraries in Chapter 24 (including the transition

from libc5 to libc6), we cover writing device drivers and kernel modules in Chapter 25,

because considerable programming energy is spent providing kernel support for the latest

whiz-bang hardware device or system services.

User interface programming takes up the next eight chapters. Two chapters cover charac-

ter-mode programming; first the hard way with termcap and termios , and then the easi-

er way using ncurses. After a quick introduction to X in Chapter 28, Chapter 29 focuses

on using the Motif and Athena widget sets. Programming X using the GTK library is

Chapter 30’s subject, followed by Qt (the foundation of KDE) in Chapter 31, and Java

programming in Chapter 32. For good measure, we also cover 3D graphics programming

using OpenGL.

The next section of the book covers three special-purpose topics. Chapter 34 examines

bash shell programming. We deal with security-related programming issues in Chapter

35, and devote Chapter 36 to debugging with gdb .

The book ends by showing you the final steps for turning your programming project over

to the world. Chapter 37 introduces you to tar and the RPM package management tool.

Documentation is essential, so we teach you how to write man pages and how to use

some SGML-based documentation tools in Chapter 38. Chapter 39, finally, looks at the

vital issue of software licensing.

Programming Toolkit P ART

I N T HIS P ART

• Overview 7

• Setting Up a Development System 13

• Using GNU cc 39

• Project Management Using GNU make 53

• Creating Self-Configuring Software with

autoconf 65

• Comparing and Merging Source Files 85

• Version Control with RCS 103

• Creating Programs in Emacs 115

The Linux

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