Beginning linux-programming

Table of Contents
Beginning Linux Programming, Second Edition.............................................................................................1
Foreword..............................................................................................................................................................5
Introduction.........................................................................................................................................................6
Welcome.................................................................................................................................................6
Who's this Book For?..............................................................................................................................6
What's Covered in the Book...................................................................................................................6
What You Need to Use this Book...........................................................................................................8
Source Code............................................................................................................................................9
Conventions............................................................................................................................................9
Tell Us What You Think.......................................................................................................................10
Why Should I Return the Reply Card?.................................................................................................10
Chapter 1: Getting Started.............................................................................................................................11
Overview...............................................................................................................................................11
What is UNIX?.....................................................................................................................................11
What is Linux?......................................................................................................................................11
Distributions..........................................................................................................................................11
The GNU Project and the Free Software Foundation...........................................................................12
Programming Linux..............................................................................................................................13
UNIX Programs....................................................................................................................................13
The C Compiler..............................................................................................................................14
Try It Out − Our First UNIX C Program........................................................................................14
How It Works..................................................................................................................................15
Getting Help..........................................................................................................................................15
Try It Out − Manual Pages and info................................................................................................16
Development System Roadmap............................................................................................................17
Programs.........................................................................................................................................17
Header Files....................................................................................................................................18
Library Files...................................................................................................................................19
Static Libraries...............................................................................................................................19
Try It Out − Static Libraries............................................................................................................20
Shared Libraries.............................................................................................................................22
UNIX Philosophy.................................................................................................................................23
Simplicity.......................................................................................................................................23
Focus..............................................................................................................................................23
Reusable Components....................................................................................................................23
Filters..............................................................................................................................................23
Open File Formats..........................................................................................................................23
Flexibility.......................................................................................................................................23
Summary...............................................................................................................................................24
Chapter 2: Shell Programming.......................................................................................................................25
Overview...............................................................................................................................................25
What is a Shell?....................................................................................................................................26
Pipes and Redirection...........................................................................................................................27
Redirecting Output.........................................................................................................................27
Redirecting Input............................................................................................................................28
Pipes...............................................................................................................................................28
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Chapter 2: Shell Programming
The Shell as a Programming Language................................................................................................29
Interactive Programs.......................................................................................................................29
Creating a Script.............................................................................................................................30
Making a Script Executable...........................................................................................................31
Shell Syntax..........................................................................................................................................32
Variables.........................................................................................................................................33
Conditions......................................................................................................................................36
Control Structures...........................................................................................................................38
Functions........................................................................................................................................49
Try It Out − A Simple Function......................................................................................................50
How It Works..................................................................................................................................50
Try It Out − Returning a Value.......................................................................................................51
How It Works..................................................................................................................................52
Commands......................................................................................................................................52
Command Execution......................................................................................................................62
Here Documents.............................................................................................................................66
Try It Out − Using Here Documents...............................................................................................66
Try It Out − Another Use for a Here Document.............................................................................67
How It Works..................................................................................................................................67
Debugging Scripts..........................................................................................................................67
Putting it All Together..........................................................................................................................68
Requirements..................................................................................................................................68
Design.............................................................................................................................................69
Try It Out − A CD Application.......................................................................................................70
Notes................................................................................................................................................76
Summary...............................................................................................................................................77
Chapter 3: Working with Files.......................................................................................................................78
Overview...............................................................................................................................................78
UNIX File Structure..............................................................................................................................78
Directories......................................................................................................................................79
Files and Devices............................................................................................................................79
System Calls and Device Drivers.........................................................................................................81
Library Functions..................................................................................................................................82
Low−level File Access..........................................................................................................................82
write.................................................................................................................................................83
read..................................................................................................................................................83
open.................................................................................................................................................84
Initial Permissions...........................................................................................................................85
umask...............................................................................................................................................86
close.................................................................................................................................................87
ioctl..................................................................................................................................................87
Try It Out − A File Copy Program..................................................................................................87
Other System Calls for Managing Files.........................................................................................89
The Standard I/O Library......................................................................................................................91
fopen................................................................................................................................................92
fread.................................................................................................................................................92
fwrite...............................................................................................................................................93
fclose...............................................................................................................................................93
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Chapter 3: Working with Files
fflush................................................................................................................................................93
fseek.................................................................................................................................................93
fgetc, getc, getchar...........................................................................................................................94
fputc, putc, putchar..........................................................................................................................94
fgets, gets.........................................................................................................................................94
Formatted Input and Output...........................................................................................................95
Other Stream Functions..................................................................................................................98
Try It Out − Another File Copy Program.......................................................................................99
Stream Errors..................................................................................................................................99
Streams and File Descriptors........................................................................................................100
File and Directory Maintenance..........................................................................................................101
chmod............................................................................................................................................101
chown............................................................................................................................................101
unlink, link, symlink......................................................................................................................101
mkdir, rmdir...................................................................................................................................102
chdir, getcwd.................................................................................................................................102
Scanning Directories...........................................................................................................................103
opendir...........................................................................................................................................103
readdir............................................................................................................................................103
telldir.............................................................................................................................................104
seekdir...........................................................................................................................................104
closedir..........................................................................................................................................104
Try It Out − A Directory Scanning Program................................................................................105
How It Works................................................................................................................................106
Errors...................................................................................................................................................107
Advanced Topics................................................................................................................................107
fcntl................................................................................................................................................108
mmap.............................................................................................................................................109
Try It Out − Using mmap.............................................................................................................110
Summary.............................................................................................................................................111
Chapter 4: The UNIX Environment............................................................................................................112
Overview.............................................................................................................................................112
Program Arguments............................................................................................................................112
Try It Out − Program Arguments.................................................................................................113
How It Works................................................................................................................................114
getopt............................................................................................................................................114
Try It Out − getopt.......................................................................................................................115
How It Works................................................................................................................................116
Environment Variables.......................................................................................................................116
Try It Out − getenv and putenv0...................................................................................................117
Use of Environment Variables.....................................................................................................118
The environ Variable....................................................................................................................119
Try It Out − environ......................................................................................................................119
How It Works................................................................................................................................119
Time and Date.....................................................................................................................................119
Try It Out − time...........................................................................................................................120
How It Works................................................................................................................................121
Try It Out − gmtime.....................................................................................................................121
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Chapter 4: The UNIX Environment
How It Works................................................................................................................................122
Try It Out − ctime.........................................................................................................................123
How It Works................................................................................................................................123
Try It Out − strftime and strptime................................................................................................125
How It Works................................................................................................................................126
Temporary Files..................................................................................................................................126
Try It Out − tmpnam and tmpfile.................................................................................................127
How It Works................................................................................................................................127
User Information.................................................................................................................................128
Try It Out − User Information.......................................................................................................129
How It Works................................................................................................................................130
Other User Information Functions...............................................................................................130
Host Information.................................................................................................................................131
Try It Out − Host Information.......................................................................................................131
How It Works................................................................................................................................132
Licensing......................................................................................................................................132
Logging...............................................................................................................................................132
Try It Out − syslog........................................................................................................................134
How It Works................................................................................................................................134
Configuring Logs.........................................................................................................................134
Try It Out − logmask.....................................................................................................................135
How It Works................................................................................................................................136
Resources and Limits..........................................................................................................................136
Try It Out − Resource Limits.......................................................................................................138
How It Works................................................................................................................................140
Summary.............................................................................................................................................140
Chapter 5: Terminals....................................................................................................................................141
Overview.............................................................................................................................................141
Reading from and Writing to the Terminal.........................................................................................141
Try It Out − Menu Routines in C..................................................................................................141
How It Works................................................................................................................................142
Why It Doesn't Quite Work...........................................................................................................143
Handling Redirected Output.........................................................................................................144
Try It Out − Checking for Output Redirection..............................................................................144
How It Works................................................................................................................................145
Talking to the Terminal................................................................................................................145
Try It Out − Using /dev/tty............................................................................................................146
The Terminal Driver and the General Terminal Interface..................................................................147
Overview......................................................................................................................................147
Hardware Model...........................................................................................................................148
The termios Structure..........................................................................................................................149
Input Modes..................................................................................................................................150
Output Modes...............................................................................................................................151
Control Modes..............................................................................................................................152
Local Modes.................................................................................................................................152
Special Control Characters...........................................................................................................153
Terminal Speed.............................................................................................................................156
Additional Functions....................................................................................................................156
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Chapter 5: Terminals
Try It Out − A Password Program with termios...........................................................................157
How It Works................................................................................................................................158
Try It Out − Reading Each Character............................................................................................158
How It Works................................................................................................................................159
Terminal Output..................................................................................................................................159
Terminal Type..............................................................................................................................159
Identify Your Terminal Type.......................................................................................................160
Using terminfo Capabilities..........................................................................................................162
Detecting Keystrokes..........................................................................................................................167
Try It Out − Your Very Own kbhit...............................................................................................167
How It Works................................................................................................................................169
Pseudo Terminals.........................................................................................................................169
Summary.............................................................................................................................................169
Chapter 6: Curses..........................................................................................................................................170
Overview.............................................................................................................................................170
Compiling with curses........................................................................................................................170
Concepts..............................................................................................................................................171
Try It Out − A Simple curses Program.........................................................................................172
Initialization and Termination.............................................................................................................173
Output to the Screen............................................................................................................................173
Reading from the Screen.....................................................................................................................174
Clearing the Screen.............................................................................................................................175
Moving the Cursor..............................................................................................................................175
Character Attributes............................................................................................................................175
Try It Out − Moving, Inserting and Attributes..............................................................................176
The Keyboard......................................................................................................................................177
Keyboard Modes..........................................................................................................................177
Keyboard Input.............................................................................................................................178
Try It Out− Keyboard Modes and Input........................................................................................178
How It Works................................................................................................................................179
Windows.............................................................................................................................................180
The WINDOW Structure..............................................................................................................180
Generalized Functions..................................................................................................................180
Moving and Updating a Window.................................................................................................181
Try It Out − Multiple Windows....................................................................................................182
Optimizing Screen Refreshes.......................................................................................................184
Subwindows........................................................................................................................................185
Try It Out − Subwindows..............................................................................................................185
How It Works................................................................................................................................187
The Keypad.........................................................................................................................................187
Try It Out − Using the Keypad.....................................................................................................188
Color...................................................................................................................................................189
Try It Out − Colors.......................................................................................................................190
Redefining Colors.........................................................................................................................191
Pads.....................................................................................................................................................191
Try It Out − Using a Pad...............................................................................................................192
The CD Collection Application..........................................................................................................193
Try It Out − A New CD Collection Application...........................................................................194
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Chapter 6: Curses
Try It Out − Looking at main........................................................................................................196
Try It Out − The Menu..................................................................................................................196
Try It Out − Database File Manipulation.....................................................................................198
Try It Out − Querying the CD Database.......................................................................................202
Summary.............................................................................................................................................206
Chapter 7: Data Management......................................................................................................................207
Overview.............................................................................................................................................207
Managing Memory..............................................................................................................................207
Simple Memory Allocation..........................................................................................................207
Try It Out − Simple Memory Allocation......................................................................................208
How It Works................................................................................................................................208
Allocating Lots of Memory..........................................................................................................208
Try It Out − Asking for all Physical Memory..............................................................................209
How It Works................................................................................................................................209
Try It Out − Available Memory....................................................................................................210
How It Works................................................................................................................................210
Abusing Memory..........................................................................................................................211
Try It Out − Abuse Your Memory................................................................................................211
How It Works................................................................................................................................212
The Null Pointer...........................................................................................................................212
Try It Out − Accessing a Null Pointer..........................................................................................212
How It Works................................................................................................................................213
How It Works................................................................................................................................213
Freeing Memory...........................................................................................................................213
Try It Out − Freeing Memory.......................................................................................................214
How It Works................................................................................................................................214
Other Memory Allocation Functions...........................................................................................214
File Locking........................................................................................................................................215
Creating Lock Files......................................................................................................................215
Try It Out − Creating a Lock File.................................................................................................216
How It Works................................................................................................................................216
Try It Out − Cooperative Lock Files............................................................................................217
How It Works................................................................................................................................218
Locking Regions...........................................................................................................................218
Use of read and write with Locking.............................................................................................221
Try It Out − Locking a File with fcntl...........................................................................................221
How It Works................................................................................................................................222
Try It Out − Testing Locks on a File.............................................................................................223
How It Works................................................................................................................................225
Competing Locks.........................................................................................................................226
Try It Out − Competing Locks.....................................................................................................226
How It Works................................................................................................................................228
Other Lock Commands................................................................................................................228
Deadlocks.....................................................................................................................................229
Databases............................................................................................................................................229
The dbm Database........................................................................................................................229
The dbm Routines........................................................................................................................230
dbm Access Functions..................................................................................................................232
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Chapter 7: Data Management
Additional dbm Functions............................................................................................................235
The CD Application............................................................................................................................237
The CD Application Using dbm...................................................................................................238
Try It Out − cd_data.h...................................................................................................................238
Try It Out − app_ui.c.....................................................................................................................239
Try It Out − cd_access.c...............................................................................................................247
Summary.............................................................................................................................................253
Chapter 8: Development Tools.....................................................................................................................254
Overview.............................................................................................................................................254
Problems of Multiple Source Files.....................................................................................................254
The make Command and Makefiles...................................................................................................255
The Syntax of Makefiles..............................................................................................................255
Options and Parameters to make..................................................................................................255
Comments in a makefile...............................................................................................................258
Macros in a makefile....................................................................................................................258
Try It Out − A Makefile with Macros...........................................................................................259
How It Works................................................................................................................................259
Multiple Targets...........................................................................................................................260
Try It Out − Multiple Targets........................................................................................................260
How It Works................................................................................................................................262
Built−in Rules..............................................................................................................................262
Suffix Rules..................................................................................................................................263
Try It Out − Suffix Rules..............................................................................................................263
How It Works................................................................................................................................264
Managing Libraries with make.....................................................................................................264
Try It Out − Managing a Library..................................................................................................264
How It Works................................................................................................................................265
Advanced Topic: Makefiles and Subdirectories..........................................................................266
GNU make and gcc......................................................................................................................266
Try It Out − gcc −MM...................................................................................................................267
How It Works................................................................................................................................267
Source Code Control...........................................................................................................................267
RCS..............................................................................................................................................267
SCCS............................................................................................................................................273
CVS..............................................................................................................................................274
Writing a Manual Page.......................................................................................................................278
Distributing Software..........................................................................................................................281
The patch Program.......................................................................................................................281
Other Distribution Utilities...........................................................................................................283
Summary.............................................................................................................................................285
Chapter 9: Debugging....................................................................................................................................286
Types of Error.....................................................................................................................................286
Specification Errors......................................................................................................................286
Design Errors................................................................................................................................286
Coding Errors...............................................................................................................................286
General Debugging Techniques..........................................................................................................287
A Program with Bugs...................................................................................................................287
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Chapter 9: Debugging
Code Inspection............................................................................................................................289
Instrumentation.............................................................................................................................290
Try It Out − Debug Information....................................................................................................291
How It Works................................................................................................................................291
Controlled Execution....................................................................................................................292
Debugging with gdb............................................................................................................................293
Starting gdb..................................................................................................................................293
Running a Program.......................................................................................................................294
Stack Trace...................................................................................................................................294
Examining Variables....................................................................................................................295
Listing the Program......................................................................................................................296
Setting Breakpoints......................................................................................................................296
Patching with the Debugger.........................................................................................................299
Learning more about gdb.............................................................................................................300
More Debugging Tools.......................................................................................................................300
Lint: Removing the Fluff from Your Programs...........................................................................301
Function Call Tools......................................................................................................................302
Execution Profiling.......................................................................................................................304
Assertions............................................................................................................................................304
Problems with assert.....................................................................................................................305
Try It Out − assert........................................................................................................................305
How It Works................................................................................................................................306
Memory Debugging............................................................................................................................306
ElectricFence................................................................................................................................307
Try It Out − ElectricFence............................................................................................................307
How It Works................................................................................................................................308
Checker.........................................................................................................................................308
Try It Out − Checker.....................................................................................................................308
How It Works................................................................................................................................309
Resources............................................................................................................................................310
Summary.............................................................................................................................................310
Chapter 10: Processes and Signals...............................................................................................................311
Overview.............................................................................................................................................311
What is a Process?..............................................................................................................................311
Process Structure.................................................................................................................................311
The Process Table........................................................................................................................313
Viewing Processes........................................................................................................................313
System Processes..........................................................................................................................314
Process Scheduling.......................................................................................................................315
Starting New Processes.......................................................................................................................316
Try It Out − system.......................................................................................................................316
How It Works................................................................................................................................317
Replacing a Process Image............................................................................................................317
Try It Out − execlp.......................................................................................................................318
How It Works................................................................................................................................319
Duplicating a Process Image.........................................................................................................319
Try It Out − fork...........................................................................................................................320
How It Works................................................................................................................................321
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Chapter 10: Processes and Signals
Waiting for a Process...................................................................................................................321
Try It Out − wait............................................................................................................................322
How It Works................................................................................................................................323
Zombie Processes.........................................................................................................................323
Try It Out − Zombies....................................................................................................................324
How It Works................................................................................................................................324
Input and Output Redirection.......................................................................................................325
Try It Out − Redirection...............................................................................................................325
How It Works................................................................................................................................326
Threads.........................................................................................................................................326
Signals.................................................................................................................................................326
Try It Out − Signal Handling.......................................................................................................328
How It Works................................................................................................................................329
Sending Signals............................................................................................................................330
Try It Out − An Alarm Clock........................................................................................................330
How It Works................................................................................................................................331
Signal Sets....................................................................................................................................334
Summary.............................................................................................................................................337
Chapter 11: POSIX Threads.........................................................................................................................338
What is a Thread?...............................................................................................................................338
Advantages and Drawbacks of Threads.......................................................................................338
Checking for Thread Support..............................................................................................................339
Try it out − POSIX compliance test..............................................................................................339
How it works.................................................................................................................................340
A First Threads Program.....................................................................................................................340
Try it out − a simple threaded program.........................................................................................342
How it works.................................................................................................................................343
Simultaneous Execution.....................................................................................................................344
Try it out − simultaneous execution of two threads......................................................................344
How it works.................................................................................................................................345
Synchronization..................................................................................................................................345
Synchronization with Semaphores...............................................................................................345
Try it out − a thread semaphore....................................................................................................347
How it works.................................................................................................................................349
Synchronization with Mutexes.....................................................................................................350
Try it out − a thread mutex............................................................................................................350
How it works.................................................................................................................................352
Thread Attributes................................................................................................................................353
detachedstate.................................................................................................................................354
schedpolicy....................................................................................................................................354
schedparam....................................................................................................................................355
inheritsched...................................................................................................................................355
scope..............................................................................................................................................355
stacksize.........................................................................................................................................355
Try it out − setting the detached state attribute.............................................................................355
How it works.................................................................................................................................356
Thread Attributes − Scheduling....................................................................................................357
Try is out − scheduling..................................................................................................................357
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Chapter 11: POSIX Threads
How it works.................................................................................................................................357
Canceling a Thread.............................................................................................................................357
Try it out − canceling a thread......................................................................................................358
How it works.................................................................................................................................360
Threads in Abundance........................................................................................................................360
Try it out − many threads..............................................................................................................360
How it works.................................................................................................................................362
Summary.............................................................................................................................................363
Chapter 12: Inter−process Communication: Pipes....................................................................................364
Overview.............................................................................................................................................364
What is a Pipe?....................................................................................................................................364
Process Pipes.......................................................................................................................................365
popen.............................................................................................................................................365
pclose.............................................................................................................................................365
Try It Out − Reading Output From an External Program............................................................365
How It Works................................................................................................................................366
Sending Output to popen..............................................................................................................366
Try It Out − Sending Output to an External Program...................................................................366
How It Works................................................................................................................................367
The Pipe Call......................................................................................................................................369
Try It Out − The pipe Function.....................................................................................................370
How It Works................................................................................................................................371
Try It Out − Pipes across a fork...................................................................................................371
How It Works................................................................................................................................372
Parent and Child Processes.................................................................................................................372
Try It Out − Pipes and exec...........................................................................................................372
How It Works................................................................................................................................373
Reading Closed Pipes...................................................................................................................374
Pipes Used as Standard Input and Output....................................................................................374
Named Pipes: FIFOs...........................................................................................................................377
Try It Out − Creating a Named Pipe.............................................................................................378
How It Works................................................................................................................................378
Accessing a FIFO.........................................................................................................................378
Try It Out − Accessing a FIFO File.............................................................................................379
How It Works................................................................................................................................379
Advanced Topic: Client/Server using FIFOs......................................................................................385
Try It Out − An Example Client/Server Application...................................................................385
How It Works................................................................................................................................388
The CD Application............................................................................................................................388
Aims.............................................................................................................................................389
Implementation.............................................................................................................................390
Try It Out − The Header File, cliserv.h.........................................................................................392
Client Interface Functions............................................................................................................393
Try It Out − The Client's Interpreter.............................................................................................393
The Server Interface.....................................................................................................................399
Try It Out − server.c......................................................................................................................399
The Pipe........................................................................................................................................402
Try It Out − Pipes Implementation Header...................................................................................402
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Chapter 12: Inter−process Communication: Pipes
Application Summary...................................................................................................................407
Summary.............................................................................................................................................407
Chapter 13: Semaphores, Message Queues and Shared Memory.............................................................409
Semaphores.........................................................................................................................................409
Semaphore Definition...................................................................................................................410
A Theoretical Example.................................................................................................................410
UNIX Semaphore Facilities.........................................................................................................411
Using Semaphores........................................................................................................................413
Try It Out − Semaphores...............................................................................................................414
How It Works................................................................................................................................416
Semaphore Summary...................................................................................................................417
Shared Memory...................................................................................................................................417
Overview......................................................................................................................................417
Shared Memory Functions...........................................................................................................418
Shared Memory Summary............................................................................................................423
Message Queues..................................................................................................................................423
Overview......................................................................................................................................424
Message Queue Functions............................................................................................................424
Message Queue Summary............................................................................................................429
The Application..................................................................................................................................429
Try It Out − Revising the Server Functions..................................................................................429
Try It Out − Revising the Client Functions...................................................................................431
IPC Status Commands........................................................................................................................433
Semaphores..................................................................................................................................433
Shared Memory............................................................................................................................433
Message Queues...........................................................................................................................433
Summary.............................................................................................................................................434
Chapter 14: Sockets.......................................................................................................................................435
Overview.............................................................................................................................................435
What is a Socket?................................................................................................................................435
Socket Connections.............................................................................................................................435
Try It Out − A Simple Local Client..............................................................................................436
Try It Out − A Simple Local Server.............................................................................................437
Socket Attributes..........................................................................................................................439
Creating a Socket..........................................................................................................................441
Socket Addresses..........................................................................................................................442
Naming a Socket..........................................................................................................................442
Creating a Socket Queue..............................................................................................................443
Accepting Connections.................................................................................................................443
Requesting Connections...............................................................................................................444
Closing a Socket...........................................................................................................................445
Socket Communications...............................................................................................................445
Try It Out − Network Client..........................................................................................................446
How It Works................................................................................................................................446
Try It Out − Network Server........................................................................................................446
How It Works................................................................................................................................447
Host and Network Byte Ordering.................................................................................................447
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Chapter 14: Sockets
Network Information..........................................................................................................................449
Try It Out − Network Information...............................................................................................450
How It Works................................................................................................................................451
Try It Out − Connecting to a Standard Service............................................................................452
How It Works................................................................................................................................453
The Internet Daemon....................................................................................................................453
Socket Options.............................................................................................................................454
Multiple Clients..................................................................................................................................454
Try It Out − A Server for Multiple Clients...................................................................................455
How It Works................................................................................................................................457
select...................................................................................................................................................457
Try It Out − select.........................................................................................................................458
How It Works................................................................................................................................460
Multiple Clients............................................................................................................................460
Try It Out − An Improved Multiple Client/Server........................................................................460
Summary.............................................................................................................................................463
Chapter 15: Tcl: Tool Command Language...............................................................................................464
Overview.............................................................................................................................................464
A Tcl Overview...................................................................................................................................464
Our First Tcl Program..................................................................................................................464
Tcl Commands.............................................................................................................................465
Variables and Values....................................................................................................................466
Quoting and Substitution..............................................................................................................467
Calculation....................................................................................................................................470
Control Structures.........................................................................................................................471
Error Handling..............................................................................................................................473
String Operations..........................................................................................................................474
Arrays...........................................................................................................................................479
Lists..............................................................................................................................................481
Procedures....................................................................................................................................486
Try It Out − Procedures................................................................................................................486
How It Works................................................................................................................................487
Input and Output...........................................................................................................................487
A Tcl Program.....................................................................................................................................491
Try It Out − A Concordance Program...........................................................................................491
How It Works................................................................................................................................493
Network Support...........................................................................................................................493
Try It Out − socket.......................................................................................................................494
How It Works................................................................................................................................494
Creating a New Tcl.............................................................................................................................494
Tcl Extensions.....................................................................................................................................494
expect............................................................................................................................................494
[incr Tcl].......................................................................................................................................495
TclX..............................................................................................................................................495
Graphics........................................................................................................................................495
Summary.............................................................................................................................................495
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Chapter 16: Programming for X..................................................................................................................496
Overview.............................................................................................................................................496
What is X?...........................................................................................................................................496
X Server.........................................................................................................................................497
X Protocol......................................................................................................................................497
Xlib................................................................................................................................................497
X Clients........................................................................................................................................497
X Toolkits.....................................................................................................................................497
X Window Manager............................................................................................................................498
The X Programming Model................................................................................................................499
Start Up.........................................................................................................................................499
Main Loop....................................................................................................................................500
Clean Up.......................................................................................................................................500
Fast Track X Programming.................................................................................................................501
The Tk Toolkit....................................................................................................................................501
Windows Programming................................................................................................................502
Try It Out − Saying Hello.............................................................................................................503
How It Works................................................................................................................................503
Configuration Files.......................................................................................................................504
More Commands..........................................................................................................................504
Tk Widgets...................................................................................................................................505
Try It Out − Learning More..........................................................................................................505
How It Works................................................................................................................................506
Tk's Built−in Dialogs...................................................................................................................529
Color Chooser................................................................................................................................529
Get Open/Save Files......................................................................................................................530
Color Schemes..............................................................................................................................531
Fonts.............................................................................................................................................532
Bindings........................................................................................................................................532
BindTags......................................................................................................................................533
Geometry Management................................................................................................................535
Focus and Navigation...................................................................................................................537
Option Database...........................................................................................................................538
Inter−application Communication................................................................................................539
Selection.......................................................................................................................................539
Clipboard......................................................................................................................................540
Window Manager.........................................................................................................................541
Dynamic/Static Loading...............................................................................................................542
Safe Tk.........................................................................................................................................543
A Mega−Widget.................................................................................................................................544
Package File Generation................................................................................................................553
An Application Using the Tree Mega−Widget...................................................................................554
Tk Process Log Viewer.......................................................................................................................556
Internationalization.......................................................................................................................566
Where Now?.................................................................................................................................567
Tix.................................................................................................................................................567
[incr Tk].........................................................................................................................................567
BLT...............................................................................................................................................567
Summary.............................................................................................................................................568
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Chapter 17: Programming GNOME using GTK+.....................................................................................569
Overview.............................................................................................................................................569
An Introduction to GNOME...............................................................................................................569
The GNOME Architecture...........................................................................................................570
The GNOME Desktop..................................................................................................................571
Programming in GNOME using GTK+.......................................................................................572
An Application in GNOME.........................................................................................................586
Summary.............................................................................................................................................594
Chapter 18: The Perl Programming Language..........................................................................................595
Overview.............................................................................................................................................595
An Introduction to Perl.................................................................................................................595
A Full Example............................................................................................................................612
Perl on the Command Line...........................................................................................................617
Modules........................................................................................................................................618
The CD Database Revisited.........................................................................................................621
Summary.............................................................................................................................................625
Chapter 19: Programming for the Internet: HTML..................................................................................626
Overview.............................................................................................................................................626
What is the World Wide Web?...........................................................................................................626
Terminology........................................................................................................................................627
The HyperText Transfer Protocol (HTTP)...................................................................................627
Multimedia Internet Mail Extensions (MIME)............................................................................627
Standard Generalized Markup Language (SGML)......................................................................627
Document Type Definition (DTD)...............................................................................................627
HyperText Markup Language (HTML).......................................................................................627
Extensible Markup Language (XML)..........................................................................................628
Cascading Style Sheets (CSS)......................................................................................................628
Extensible Hypertext Markup Language (XHTML)....................................................................628
Uniform Resource Locator (URL)...............................................................................................628
Uniform Resource Identifier (URI)..............................................................................................628
Writing HTML....................................................................................................................................629
Try It Out − A Simple HTML Document....................................................................................629
How It Works................................................................................................................................629
A More Formal Look at HTML..........................................................................................................630
HTML Tags..................................................................................................................................631
Images..........................................................................................................................................637
Try It Out − Adding an Image......................................................................................................638
How It Works................................................................................................................................639
Tables...........................................................................................................................................639
Try It Out − A Table....................................................................................................................640
How It Works................................................................................................................................640
Try It Out − Another Table...........................................................................................................641
How It Works................................................................................................................................642
Anchors or Hyperlinks.................................................................................................................642
Try It Out − Anchors....................................................................................................................643
How It Works................................................................................................................................644
Combining Anchors and Images..................................................................................................644
Try It Out − Images as Anchors...................................................................................................644
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