Description
Book SynopsisA compendium of shell scripting recipes that can immediately be used or adjusted The Shell is the primary way of communicating with Unix and Linux and provides a direct way to program the system by automating simple-to-intermediate tasks.
Table of ContentsIntroduction xxix
Part I: About the Ingredients
Chapter 1: The History of Unix, Gnu, and Linux 3
Unix 3
“Everything is a File” and Pipelines 5
BSD 6
GNU 7
Linux 11
Summary 12
Chapter 2: Getting Started 15
Choosing an OS 15
GNU/Linux 15
The BSDs 17
Proprietary Unix 17
Microsoft Windows 17
Choosing an Editor 18
Graphical Text Editors 18
Terminal Emulation 21
Nongraphical Text Editors 22
Setting Up the Environment 24
The Shell Profile 24
Aliases 26
vim Settings 30
Summary 31
Chapter 3: Variables 33
Using Variables 33
Typing 34
Assigning Values to Variables 35
Positional Parameters 39
Return Codes 42
Unsetting Variables 45
Preset and Standard Variables 47
BASH_ENV 47
BASHOPTS 47
SHELLOPTS 48
BASH_COMMAND 50
BASH_SOURCE, FUNCNAME, LINENO, and BASH_LINENO 51
SHELL 55
HOSTNAME and HOSTTYPE 55
Working Directory 55
PIPESTATUS 55
TIMEFORMAT 56
PPID 57
RANDOM 58
REPLY 58
SECONDS 58
BASH_XTRACEFD 59
GLOBIGNORE 60
HOME 62
IFS 62
PATH 63
TMOUT 64
TMPDIR 65
User Identification Variables 65
Summary 66
Chapter 4: Wildcard Expansion 67
Filename Expansion (Globbing) 67
Bash Globbing Features 70
Shell Options 71
Regular Expressions and Quoting 75
Overview of Regular Expressions 76
Quoting 77
Summary 81
Chapter 5: Conditional Execution 83
If/Then 83
Else 85
elif 85
Test ([) 87
Flags for Test 88
File Comparison Tests 95
String Comparison Tests 96
Regular Expression Tests 98
Numerical Tests 101
Combining Tests 103
Case 105
Summary 109
Chapter 6: Flow Control Using Loops 111
For Loops 111
When to Use for Loops 112
Imaginative Ways of Feeding “for” with Data 112
C-Style for Loops 118
while Loops 119
When to Use while Loops 119
Ways to Use while Loops 119
Nested Loops 125
Breaking and Continuing Loop Execution 126
while with Case 130
until Loops 131
select Loops 133
Summary 137
Chapter 7: Variables Continued 139
Using Variables 139
Variable Types 141
Length of Variables 142
Special String Operators 144
Stripping Variable Strings by Length 144
Stripping from the End of the String 146
Stripping Strings with Patterns 147
Searching Strings 151
Using Search and Replace 151
Replacing Patterns 153
Deleting Patterns 153
Changing Case 153
Providing Default Values 153
Indirection 157
Sourcing Variables 158
Summary 159
Chapter 8: Functions and Libraries 161
Functions 161
Defining Functions 162
Function Output 162
Writing to a File 164
Redirecting the Output of an Entire Function 167
Functions with Trap 171
Recursive Functions 173
Variable Scope 177
Libraries 181
Creating and Accessing Libraries 183
Library Structures 183
Network Configuration Library 187
Use of Libraries 191
getopts 191
Handling Errors 194
getopts within Functions 195
Summary 197
Chapter 9: Arrays 199
Assigning Arrays 199
One at a Time 200
All at Once 200
By Index 201
All at Once from a Source 201
Read from Input 203
Accessing Arrays 205
Accessing by Index 205
Length of Arrays 206
Accessing by Variable Index 206
Selecting Items from an Array 209
Displaying the Entire Array 209
Associative Arrays 210
Manipulating Arrays 211
Copying an Array 211
Appending to an Array 213
Deleting from an Array 214
Advanced Techniques 216
Summary 217
Chapter 10: Processes 219
The ps Command 219
ps Line Length 220
Parsing the Process Table Accurately 220
killall 223
The /proc pseudo-filesystem 225
prtstat 226
I/O Redirection 227
Appending Output to an Existing File 229
Permissions on Redirections 229
exec 229
Using exec to Replace the Existing Program 230
Using exec to Change Redirection 231
Pipelines 237
Background Processing 237
wait 238
Catching Hangups with nohup 239
Other Features of /proc and /sys 242
Version 242
SysRq 242
/proc/meminfo 245
/proc/cpuinfo 245
/sys 246
/sys/devices/system/node 251
sysctl 253
Summary 254
Chapter 11: Choosing and Using Shells 255
The Bourne Shell 256
The KornShell 256
The C Shell 256
The Tenex C Shell 257
The Z Shell 257
The Bourne Again Shell 257
The Debian Almquist Shell 258
Dotfiles 258
Interactive Login Shells 259
Interactive Non-Login Shells 260
Non-Interactive Shells 261
Logout Scripts 262
Command Prompts 262
The PS1 Prompt 262
The PS2, PS3, and PS4 Prompts 264
Aliases 265
Timesavers 265
Modifying Behaviors 265
History 266
Recalling Commands 267
Searching History 267
Timestamps 268
Tab Completion 269
ksh 269
tcsh 270
zsh 270
bash 271
Foreground, Background, and Job Control 272
Backgrounding Processes 272
Job Control 273
nohup and disown 275
Summary 276
Part II: Recipes For Using and Extending System Tools
Chapter 12: File Manipulation 279
stat 279
cat 281
Numbering Lines 282
Dealing with Blank Lines 282
Non-Printing Characters 283
cat Backwards is tac 284
Redirection 285
Redirecting Output: The Single Greater-Than Arrow (>) 285
Appending: The Double Greater-Than Arrow (>>) 286
Input Redirection: The Single Less-Than Arrow (<) 288
Here Documents: The Double Less-Than Arrow (<< EOF) 290
dd 292
df 294
mktemp 295
join 297
install 298
grep 300
grep Flags 300
grep Regular Expressions 301
split 303
tee 304
touch 306
find 307
find-exec 310
Summary 313
Chapter 13: Text Manipulation 315
cut 315
echo 316
dial1 316
dial2 319
fmt 320
head and tail 323
Prizes 323
World Cup 324
od 328
paste 331
pr 334
printf 335
shuf 337
Dice Thrower 337
Card Dealer 338
Travel Planner 340
sort 341
Sorting on Keys 342
Sorting Log Files by Date and Time 344
Sorting Human-Readable Numbers 345
tr 346
uniq 350
wc 351
Summary 352
Chapter 14: Tools For Systems Administration 353
basename 353
date 355
Typical Uses of date 355
More Interesting Uses of date 359
dirname 360
factor 362
identity, groups, and getent 364
logger 367
md5sum 368
mkfi fo 370
Master and Minions 371
Reversing the Order 373
Networking 375
telnet 376
netcat 376
ping 378
Scripting ssh and scp 381
OpenSSL 383
nohup 390
seq 391
Integer Sequences 391
Floating Point Sequences 393
sleep 394
timeout 394
Shutdown Script 396
Network Timeout 399
uname 400
uuencode 401
xargs 402
yes 405
Summary 406
Part III: Recipes For Systems Administration
Chapter 15: Shell Features 409
Recipe 15-1: Installing Init Scripts 409
Technologies Used 410
Concepts 410
Potential Pitfalls 410
Structure 410
Recipe 412
Invocation 414
Summary 414
Recipe 15-2: RPM Report 414
Technologies Used 415
Concepts 415
Potential Pitfalls 415
Structure 415
Recipe 417
Invocation 419
Summary 420
Recipe 15-3: Postinstall Scripts 421
Technologies Used 421
Concepts 421
Potential Pitfalls 422
Structure 422
Recipe 423
Invocation 425
Summary 426
Chapter 16: Systems Administration 427
Recipe 16-1: init Scripts 427
Technologies Used 428
Concepts 428
Potential Pitfalls 429
Structure 430
Recipe 431
Invocation 432
Summary 433
Recipe 16-2: CGI Scripts 433
Technologies Used 433
Concepts 434
Potential Pitfalls 434
Structure 435
Recipe 438
Invocation 441
Summary 445
Recipe 16-3: Configuration Files 445
Technologies Used 445
Concepts 445
Potential Pitfalls 446
Structure 446
Recipe 446
Invocation 447
Summary 448
Recipe 16-4: Locks 448
Technologies Used 448
Concepts 448
Potential Pitfalls 449
Structure 450
Recipe 453
Invocation 455
Summary 458
Chapter 17: Presentation 459
Recipe 17-1: Space Game 459
Technologies Used 459
Concepts 460
Potential Pitfalls 462
Structure 462
Recipe 464
Invocation 469
Summary 470
Chapter 18: Data Storage and Retrieval 471
Recipe 18-1: Parsing HTML 471
Technologies Used 471
Concepts 472
Potential Pitfalls 472
Structure 472
Recipe 473
Invocation 474
Summary 476
Recipe 18-2: CSV Formatting 476
Technologies Used 476
Concepts 476
Potential Pitfalls 477
Structure 477
Recipe 478
Invocation 480
Summary 481
Chapter 19: Numbers 483
Recipe 19-1: The Fibonacci Sequence 483
Technologies Used 483
Concepts 484
Potential Pitfalls 484
Structure for Method 1 485
Recipe for Method 1 486
Invocation of Method 1 486
Structure for Method 2 487
Recipes for Method 2 488
Invocations of Method 2 489
Structure for Method 3 490
Recipe for Method 3 490
Invocation of Method 3 491
Summary 492
Recipe 19-2: PXE Booting 492
Technologies Used 492
Concepts 493
Potential Pitfalls 493
Structure 493
Recipe 494
Invocation 497
Summary 499
Chapter 20: Processes 501
Recipe 20-1: Process Control 501
Technologies Used 501
Concepts 502
Potential Pitfalls 503
Structure 503
Recipe 506
Invocation 511
Summary 516
Chapter 21: Internationalization 517
Recipe 21-1: Internationalization 517
Technologies Used 518
Concepts 518
Potential Pitfalls 519
Structure 520
Recipe 521
Invocation 525
Summary 526
Part IV: Reference
Appendix: Further Reading 529
Shell Tutorials and Documentation 529
Arrays 530
Tools 530
Unix Flavors 531
Shell Services 531
Glossary 533
Index 539
