UNIX Shell programming. Kochan, Patrick Wood

456 Pages·2003·2.872 MB·English

by  Kochan, Stephen G;Wood, Patrick H

Stephen G. Kochan
Patrick Wood
Unix Shell
Programming
Third Edition
800 East 96th Street, Indianapolis, Indiana 46240
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Contents at a Glance
1 Introduction.................................................................................................1
2 A Quick Review of the Basics.......................................................................5
3 What Is the Shell?.......................................................................................41
4 Tools of the Trade.......................................................................................53
5 And Away We Go........................................................................................99
6 Can I Quote You on That?.......................................................................115
7 Passing Arguments....................................................................................133
8 Decisions, Decisions.................................................................................145
9 ‘Round and ‘Round She Goes...................................................................183
10 Reading and Printing Data.......................................................................209
11 Your Environment....................................................................................235
12 More on Parameters..................................................................................267
13 Loose Ends................................................................................................287
14 Rolo Revisited...........................................................................................307
15 Interactive and Nonstandard Shell Features............................................325
A Shell Summary..........................................................................................363
B For More Information...............................................................................403
Index.........................................................................................................407
Table of Contents
1 Introduction 1
2 AQuick Review of the Basics 5
Some Basic Commands ...............................................................................5
Displaying the Date and Time:
The date Command .........................................................................5
Finding Out Who’s Logged In: The who Command ........................5
Echoing Characters: The echo Command .........................................6
Working with Files .......................................................................................6
Listing Files: The ls Command ..........................................................7
Displaying the Contents of a File: The cat Command .....................7
Counting the Number of Words in a File: The wc Command .........8
Command Options ............................................................................8
Making a Copy of a File: The cp Command .....................................9
Renaming a File: The mv Command .................................................9
Removing a File: The rm Command ...............................................10
Working with Directories ..........................................................................10
The Home Directory and Pathnames ..............................................11
Displaying Your Working Directory: The pwd Command ..............12
Changing Directories: The cd Command ........................................13
More on the ls Command ...............................................................16
Creating a Directory: The mkdir Command ...................................18
Copying a File from One Directory to Another ..............................18
Moving Files Between Directories ....................................................19
Linking Files: The ln Command ......................................................20
Removing a Directory: The rmdir Command .................................24
Filename Substitution ................................................................................24
The Asterisk ......................................................................................24
Matching Single Characters .............................................................26
Standard Input/Output and I/O Redirection ............................................28
Standard Input and Standard Output ..............................................28
Output Redirection ..........................................................................30
Input Redirection .............................................................................32
Pipes ...........................................................................................................33
Filters ................................................................................................35
Standard Error ............................................................................................35
More on Commands .................................................................................36
Typing More Than One Command on a Line ................................36
Sending a Command to the Background ........................................36
The ps Command .............................................................................37
Command Summary .................................................................................38
Exercises .....................................................................................................38
3 What Is the Shell? 41
The Kernel and the Utilities ......................................................................41
The Login Shell ..........................................................................................42
Typing Commands to the Shell ................................................................45
The Shell’s Responsibilities ........................................................................46
Program Execution ...........................................................................46
Variable and Filename Substitution .................................................48
I/O Redirection .................................................................................49
Pipeline Hookup ...............................................................................51
Environment Control .......................................................................51
Interpreted Programming Language ................................................52
4 Tools of the Trade 53
Regular Expressions ...................................................................................53
Matching Any Character: The Period (.) .........................................54
Matching the Beginning of the Line: The Caret (^) ........................55
Matching the End of the Line: The Dollar Sign ($) ........................55
Matching a Choice of Characters: The [...] Construct ....................57
Matching Zero or More Characters: The Asterisk (*) .......................59
Matching a Precise Number of Characters: \{...\} ...........................62
Saving Matched Characters: \(...\) ..................................................64
cut ..............................................................................................................67
The -d and -f Options ......................................................................69
paste ...........................................................................................................72
The -d Option ...................................................................................73
The -s Option ...................................................................................74
sed ..............................................................................................................74
The -n Option ..................................................................................76
Deleting Lines ...................................................................................77
vi UNIX SHELL PROGRAMMING
tr .................................................................................................................78
The -s Option ...................................................................................81
The –d Option ..................................................................................82
grep ............................................................................................................83
Regular Expressions and grep ..........................................................86
The -v Option ...................................................................................87
The -l Option ....................................................................................88
The -n Option ..................................................................................89
sort .............................................................................................................89
The -u Option ...................................................................................90
The -r Option ...................................................................................90
The -o Option ...................................................................................90
The -n Option ..................................................................................91
Skipping Fields .................................................................................92
The -t Option ...................................................................................92
Other Options ..................................................................................93
uniq ............................................................................................................94
The -d Option ...................................................................................95
Other Options ..................................................................................96
Exercises .....................................................................................................97
5 And Away We Go 99
Command Files ..........................................................................................99
Comments ......................................................................................102
Variables ...................................................................................................103
Displaying the Values of Variables .................................................104
The Null Value ................................................................................107
Filename Substitution and Variables .............................................108
The ${variable} Construct ..............................................................110
Built-in Integer Arithmetic ......................................................................110
Exercises ...................................................................................................112
6 Can I Quote You on That? 115
The Single Quote .....................................................................................115
The Double Quote ...................................................................................119
The Backslash ..........................................................................................121
Using the Backslash for Continuing Lines ....................................122
The Backslash Inside Double Quotes .............................................123
Contents vii
Command Substitution ...........................................................................124
The Back Quote ..............................................................................124
The $(...) Construct ........................................................................125
The expr Command .......................................................................129
Exercises ...................................................................................................131
7 Passing Arguments 133
The $# Variable ..............................................................................134
The $* Variable ...............................................................................135
A Program to Look Up Someone in the Phone Book ....................136
A Program to Add Someone to the Phone Book ...........................138
A Program to Remove Someone from the Phone Book ................139
${n} .................................................................................................141
The shift Command ................................................................................141
Exercises ...................................................................................................143
8 Decisions, Decisions 145
Exit Status ................................................................................................145
The $? Variable ...............................................................................146
The test Command ..................................................................................149
String Operators .............................................................................150
An Alternative Format for test .......................................................154
Integer Operators ...........................................................................155
File Operators .................................................................................157
The Logical Negation Operator ! ...................................................158
The Logical AND Operator –a ........................................................158
Parentheses .....................................................................................159
The Logical OR Operator –o ...........................................................159
The else Construct ...................................................................................160
The exit Command .................................................................................162
A Second Look at the rem Program ...............................................163
The elif Construct ....................................................................................164
Yet Another Version of rem ...........................................................167
The case Command .................................................................................169
Special Pattern Matching Characters .............................................171
The -x Option for Debugging Programs ........................................173
Back to the case ..............................................................................175
The Null Command : ..............................................................................177
The && and || Constructs ........................................................................177
Exercises ...................................................................................................180
viii UNIX SHELL PROGRAMMING
9 ’Round and ’Round She Goes 183
The for Command ...................................................................................183
The $@ Variable ..............................................................................187
The for Without the List ................................................................188
The while Command .....................................................................189
The until Command ................................................................................191
More on Loops .........................................................................................196
Breaking Out of a Loop ..................................................................196
Skipping the Remaining Commands in a Loop ............................198
Executing a Loop in the Background ............................................199
I/O Redirection on a Loop .............................................................199
Piping Data Into and Out of a Loop ..............................................200
Typing a Loop on One Line ...........................................................200
The getopts Command ............................................................................201
Exercises ...................................................................................................205
10 Reading and Printing Data 209
The read Command .................................................................................209
A Program to Copy Files ................................................................209
Special echo Escape Characters ......................................................212
An Improved Version of mycp .......................................................212
A Final Version of mycp .................................................................214
A Menu-Driven Phone Program ....................................................219
The $$ Variable and Temporary Files ............................................224
The Exit Status from read ...............................................................225
The printf Command ..............................................................................228
Exercises ...................................................................................................233
11 Your Environment 235
Local Variables .........................................................................................235
Subshells .........................................................................................236
Exported Variables ...................................................................................237
export -p .........................................................................................241
PS1 and PS2 .............................................................................................241
HOME, James ...........................................................................................242
Your PATH ................................................................................................243
Your Current Directory ............................................................................251
CDPATH ..........................................................................................252
Contents ix
More on Subshells ...................................................................................253
The . Command .............................................................................254
The exec Command .......................................................................257
The (...) and { ...; } Constructs ........................................................258
Another Way to Pass Variables to a Subshell .................................262
Your .profile File ......................................................................................262
The TERM Variable ..................................................................................264
The TZ Variable ........................................................................................264
Exercises ...................................................................................................265
12 More on Parameters 267
Parameter Substitution ............................................................................267
${parameter} ...................................................................................268
${parameter:-value} ........................................................................268
${parameter:=value} ........................................................................269
${parameter:?value} ........................................................................270
${parameter:+value} ........................................................................270
Pattern Matching Constructs .........................................................270
${#variable} .....................................................................................273
The $0 Variable ........................................................................................273
The set Command ...................................................................................274
The -x Option .................................................................................274
set with No Arguments ..................................................................275
Using set to Reassign Positional Parameters ..................................276
The -- Option ..................................................................................277
Other Options to set ......................................................................280
The IFS Variable .......................................................................................280
The readonly Command .........................................................................283
The unset Command ...............................................................................284
Exercises ...................................................................................................284
13 Loose Ends 287
The eval Command .................................................................................287
The wait Command .................................................................................289
The $! Variable ...............................................................................290
The trap Command .................................................................................290
trap with No Arguments ................................................................292
Ignoring Signals ..............................................................................292
Resetting Traps ...............................................................................293