Table of Contents
Preface xv
Chapter 1 Introduction 1
What is Unix? 2
Available Shell Types 2
What is bash? 3
Getting help for bash Commands 4
Navigating Around Directories 4
The history Command 4
Listing Filenames with the Is Command 5
Displaying Contents of Files 8
The cat Command 8
The head and tail Commands 9
The Pipe Symbol 10
The fold Command 11
File Ownership: Owner, Group, and World 11
Hidden Files 12
Handling Problematic Filenames 13
Working with Environment Variables 13
The env Command 13
Useful Environment Variables 14
Setting the PATH Environment Variable 14
Specifying Aliases and Environment Variables 15
Finding Executable Files 16
The printf Command and the echo Command 17
The cut Command 17
The echo Command and Whitespaces 18
Command Substitution ("backtick") 20
The pipe" Symbol and Multiple Commands 20
Using a Semicolon to Separate Commands 21
The paste Command 22
Inserting Blank Lines with the paste Command 22
A Simple Use Case with the paste Command 23
A Simple Use Case with cut and paste Commands 24
What about zsh? 25
Switching between bash and zsh 26
Configuring zsh 26
Summary 26
Chapter 2 Files and Directories 29
Create, Copy, Remove, and Move Files 29
Creating Text Files 29
Copying Files 30
Copy Files with Command Substitution 30
Deleting Files 31
Moving Files 32
The In Command 32
The basename, dirname, and file Commands 33
The wc Command 33
The cat Command 34
The more Command and the less Command 34
The head Command 35
The tail Command 36
Comparing File Contents 38
The Parts of a Filename 38
Working with File Permissions 39
The chmod Command 40
Changing owner, permissions, and groups 40
The umask and ulimit Commands 41
Working with Directories 41
Absolute and Relative Directories 41
Absolute/Relative Pathnames 41
Creating Directories 42
Removing Directories 43
Navigating to Directories 43
Moving Directories 44
Using Quote Characters 44
Streams and Redirection Commands 45
Working with Metacharacters 46
Working with Character Classes 47
Metacharacters and Character Classes 48
Digits and Characters 48
Working with "^" and "\" and "!" 49
Filenames and Metacharacters 49
Summary 50
Chapter 3 Useful Commands 51
The join Command 52
The fold Command 52
The split Command 53
The sort Command 53
The uniq Command 56
How to Compare Files 56
The od Command 57
The tr Command 57
A Simple Use Case 60
The find Command 61
The tee Command 62
File Compression Commands 63
The tar command 63
The cpio Command 63
The gzip and gunzip Commands 64
The bunzip2 Command 64
The zip Command 65
Commands for zip Files and bz Files 65
Internal Field Separator (IFS) 65
Data From a Range of Columns in a Dataset 66
Working with Uneven Rows in Datasets 68
Summary 68
Chapter 4 Conditional Logic and Loops 71
Quick Overview of Operators in bash 71
Arithmetic Operations and Operators 72
The expr Command 72
Arithmetic Operators 73
Boolean and Numeric Operators 73
Compound Operators and Numeric Operators 74
Working with Variables 74
Assigning Values to Variables 75
The read Command for User Input 76
Boolean Operators and String Operators 76
Compound Operators and String Operators 77
File Test Operators 78
Compound Operators and File Operators 79
Conditional Logic with if /else/fi Statements 80
The case/esac Statement 81
Working with Strings in Shell Scripts 84
Working with Loops 85
Using a for loop 85
Checking Files in a Directory 86
Working with Nested Loops 87
Using a while Loop 89
The while, case, and if/elif/else/fi Statements 91
Using an until Loop 92
User-defined Functions 92
Creating a Simple Menu from Shell Commands 94
Arrays in bash 96
Working with Arrays 98
Summary 102
Chapter 5 Filtering Data with grep 103
What is the grep Command? 104
Metacharacters and the grep Command 105
Escaping Metacharacters with the grep Command 105
Useful Options for the grep Command 106
Character Classes and the grep Command 110
Working with the -c Option in grep 111
Matching a Range of Lines 112
Using Back References in the grep Command 114
Finding Empty lines in Datasets 116
Using Keys to Search Datasets 116
The Backslash Character and the grep Command 117
Multiple Matches in the grep Command 117
The grep Command and the xargs Command 118
Searching zip Files for a String 119
Checking for a Unique Key Value 120
Redirecting Error Messages 121
The egrep Command and fgrep Command 121
Displaying "Pure" Words in a Dataset with egrep 121
The fgrep Command 123
A Simple Use Case 123
Summary 125
Chapter 6 Transforming Data with sed 127
What is the sed Command? 127
The sed Execution Cycle 128
Matching String Patterns Using sed 128
Substituting String Patterns Using sed 129
Replacing Vowels from a String or a File 130
Deleting Multiple Digits and Letters from a String 131
Search and Replace with sed 131
Datasets with Multiple Delimiters 133
Useful Switches in sed 134
Working with Datasets 135
Printing Lines 135
Character Classes and sed 136
Removing Control Characters 137
Counting Words in a Dataset 137
Back References in sed 138
Displaying Only "Pure" Words in a Dataset 139
One Line sed Commands 140
Summary 147
Chapter 7 Working with awk 149
The awk Command 150
Built-in Variables That Control awk 150
How Does the awk Command Work? 151
Aligning Text with the printf Command 152
Conditional Logic and Control Statements 152
The while Statement 153
A for loop in awk 154
A for loop with a break Statement 154
The next and continue Statements 155
Deleting Alternate Lines in Datasets 155
Merging Lines in Datasets 156
Printing File Contents as a Single Line 156
Joining Groups of Lines in a Text File 157
Joining Alternate Lines in a Text File 158
Matching with Metacharacters and Character Sets 159
Printing Lines Using Conditional Logic 160
Splitting Filenames with awk 161
Working with Postfix Arithmetic Operators 161
Numeric Functions in awk 162
One Line awk Commands 165
Useful Short awk Scripts 166
Printing the Words in a Text String in awk 167
Count Occurrences of a String in Specific Rows 167
Printing a String in a Fixed Number of Columns 169
Printing a Dataset in a Fixed Number of Columns 169
Aligning Columns in Datasets 170
Aligning Columns and Multiple Rows in Datasets 171
Removing a Column from a Text File 173
Subsets of Columns Aligned Rows in Datasets 173
Counting Word Frequency in Datasets 175
Displaying Only "Pure" Words in a Dataset 176
Working with Multiline Records in awk 178
A Simple Use Case 179
Another Use Case 181
Summary 183
Chapter 8 Intro to Shell Scripts 185
What are Shell Scripts? 186
A Simple Shell Script 186
Setting Environment Variables via Shell Scripts 187
Sourcing or "Dotting" a Shell Script 188
Working with Functions in Shell Scripts 189
Passing values to Functions in a Shell Script (1) 190
Passing values to Functions in a Shell Script (2) 191
Iterate through values passed to a Function 192
Positional Parameters in User-defined Functions 196
Shell Scripts, Functions, and User Input 198
Recursion and Shell Scripts 199
Iterative Solutions for Factorial Values 200
Calculating Fibonacci Numbers 203
Calculating the GCD of Two Positive Integers 204
Calculating the LCM of two Positive Integers 205
Calculating Prime Divisors 207
Summary 208
Chapter 9 Shell Scripts with grep and awk Command 209
The grep Command with zip Files 209
The grep Command with Multiple Files 212
Simulating Relational Data with the grep Command 216
Checking Updates in a Logfile 218
Processing Multiline Records 220
Adding the Contents of Records 221
Using the split Function in awk 221
Scanning Diagonal Elements in Datasets 222
Adding Values From Multiple Datasets (1) 225
Adding Values From Multiple Datasets (2) 226
Adding Values From Multiple Datasets (3) 228
Calculating Combinations of Field Values 229
Summary 230
Chapter 10 Miscellaneous Shell Scripts 231
Ushig rm and mv with Directories 231
Using the find Command with Directories 233
Creating a Directory of Directories 233
Cloning a set of Sub-directories 234
Executing Files in Multiple Directories 238
The case/esac Command 239
Compressing/uncompressing Files 241
The dd Command 241
The crontab Command 242
Uncompressing Files as a cron Job 243
Scheduled Commands and Background Processes 244
How to Schedule Tasks 244
The nohup Command 244
Executing Commands Remotely 244
How to Schedule Tasks in the Background 245
How to Terminate Processes 245
Terminating Multiple Processes 245
Process-Related Commands 246
How to Monitor Processes 246
Checking Execution Results 247
System Messages and Log Files 249
Disk Usage Commands 250
Trapping and Ignoring Signals 250
Arithmetic with the bc and dc Commands 251
Working with the date Command 252
Print-related Commands 255
Creating a Report with the print f () Command 255
Checking Updates hi a Logfile 256
Listing Active Users on a Machine 258
Miscellaneous Commands 259
Summary 261
Index 263
