bash Cookbook | O'Reilly Media

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bash Cookbook Solutions and Examples for bash Users By Carl Albing, JP Vossen, Cameron Newham
May 2007
Pages: 622

| Table of Contents | Index | Sample Chapter | Colophon

Chapter 1 Beginning bash
1. Why bash?
2. The bash Shell
3. Decoding the Prompt
4. Showing Where You Are
5. Finding and Running Commands
6. Getting Information About Files
7. Showing All Hidden (dot) Files in the Current Directory
8. Using Shell Quoting
9. Using or Replacing Built-ins and External Commands
10. Determining If You Are Running Interactively
11. Setting bash As Your Default Shell
12. Getting bash for Linux
13. Getting bash for xBSD
14. Getting bash for Mac OS X
15. Getting bash for Unix
16. Getting bash for Windows
17. Getting bash Without Getting bash
18. Learning More About bash Documentation
Chapter 2 Standard Output
1. Writing Output to the Terminal/Window
2. Writing Output but Preserving Spacing
3. Writing Output with More Formatting Control
4. Writing Output Without the Newline
5. Saving Output from a Command
6. Saving Output to Other Files
7. Saving Output from the ls Command
8. Sending Both Output and Error Messages to Different Files
9. Sending Both Output and Error Messages to the Same File
10. Appending Rather Than Clobbering Output
11. Using Just the Beginning or End of a File
12. Skipping a Header in a File
13. Throwing Output Away
14. Saving or Grouping Output from Several Commands
15. Connecting Two Programs by Using Output As Input
16. Saving a Copy of Output Even While Using It As Input
17. Connecting Two Programs by Using Output As Arguments
18. Using Multiple Redirects on One Line
19. Saving Output When Redirect Doesn't Seem to Work
20. Swapping STDERR and STDOUT
21. Keeping Files Safe from Accidental Overwriting
22. Clobbering a File on Purpose
Chapter 3 Standard Input
1. Getting Input from a File
2. Keeping Your Data with Your Script
3. Preventing Weird Behavior in a Here-Document
4. Indenting Here-Documents
5. Getting User Input
6. Getting Yes or No Input
7. Selecting from a List of Options
8. Prompting for a Password
Chapter 4 Executing Commands
1. Running Any Executable
2. Telling If a Command Succeeded or Not
3. Running Several Commands in Sequence
4. Running Several Commands All at Once
5. Deciding Whether a Command Succeeds
6. Using Fewer if Statements
7. Running Long Jobs Unattended
8. Displaying Error Messages When Failures Occur
9. Running Commands from a Variable
10. Running All Scripts in a Directory
Chapter 5 Basic Scripting: Shell Variables
1. Documenting Your Script
2. Embedding Documentation in Shell Scripts
3. Promoting Script Readability
4. Separating Variable Names from Surrounding Text
5. Exporting Variables
6. Seeing All Variable Values
7. Using Parameters in a Shell Script
8. Looping Over Arguments Passed to a Script
9. Handling Parameters with Blanks
10. Handling Lists of Parameters with Blanks
11. Counting Arguments
12. Consuming Arguments
13. Getting Default Values
14. Setting Default Values
15. Using null As a Valid Default Value
16. Using More Than Just a Constant String for Default
17. Giving an Error Message for Unset Parameters
18. Changing Pieces of a String
19. Using Array Variables
Chapter 6 Shell Logic and Arithmetic
1. Doing Arithmetic in Your Shell Script
2. Branching on Conditions
3. Testing for File Characteristics
4. Testing for More Than One Thing
5. Testing for String Characteristics
6. Testing for Equal
7. Testing with Pattern Matches
8. Testing with Regular Expressions
9. Changing Behavior with Redirections
10. Looping for a While
11. Looping with a read
12. Looping with a Count
13. Looping with Floating-Point Values
14. Branching Many Ways
15. Parsing Command-Line Arguments
16. Creating Simple Menus
17. Changing the Prompt on Simple Menus
18. Creating a Simple RPN Calculator
19. Creating a Command-Line Calculator
Chapter 7 Intermediate Shell Tools I
1. Sifting Through Files for a String
2. Getting Just the Filename from a Search
3. Getting a Simple True/False from a Search
4. Searching for Text While Ignoring Case
5. Doing a Search in a Pipeline
6. Paring Down What the Search Finds
7. Searching with More Complex Patterns
8. Searching for an SSN
9. Grepping Compressed Files
10. Keeping Some Output, Discarding the Rest
11. Keeping Only a Portion of a Line of Output
12. Reversing the Words on Each Line
13. Summing a List of Numbers
14. Counting String Values
15. Showing Data As a Quick and Easy Histogram
16. Showing a Paragraph of Text After a Found Phrase
Chapter 8 Intermediate Shell Tools II
1. Sorting Your Output
2. Sorting Numbers
3. Sorting IP Addresses
4. Cutting Out Parts of Your Output
5. Removing Duplicate Lines
6. Compressing Files
7. Uncompressing Files
8. Checking a tar Archive for Unique Directories
9. Translating Characters
10. Converting Uppercase to Lowercase
11. Converting DOS Files to Linux Format
12. Removing Smart Quotes
13. Counting Lines, Words, or Characters in a File
14. Rewrapping Paragraphs
15. Doing More with less
Chapter 9 Finding Files: find, locate, slocate
1. Finding All Your MP3 Files
2. Handling Filenames Containing Odd Characters
3. Speeding Up Operations on Found Files
4. Finding Files Across Symbolic Links
5. Finding Files Irrespective of Case
6. Finding Files by Date
7. Finding Files by Type
8. Finding Files by Size
9. Finding Files by Content
10. Finding Existing Files and Content Fast
11. Finding a File Using a List of Possible Locations
Chapter 10 Additional Features for Scripting
1. "Daemon-izing" Your Script
2. Reusing Code with Includes and Sourcing
3. Using Configuration Files in a Script
4. Defining Functions
5. Using Functions: Parameters and Return Values
6. Trapping Interrupts
7. Redefining Commands with alias
8. Avoiding Aliases, Functions
Chapter 11 Working with Dates and Times
1. Formatting Dates for Display
2. Supplying a Default Date
3. Automating Date Ranges
4. Converting Dates and Times to Epoch Seconds
5. Converting Epoch Seconds to Dates and Times
6. Getting Yesterday or Tomorrow with Perl
7. Figuring Out Date and Time Arithmetic
8. Handling Time Zones, Daylight Saving Time, and Leap Years
9. Using date and cron to Run a Script on the Nth Day
Chapter 12 End-User Tasks As Shell Scripts
1. Starting Simple by Printing Dashes
2. Viewing Photos in an Album
3. Loading Your MP3 Player
4. Burning a CD
5. Comparing Two Documents
Chapter 13 Parsing and Similar Tasks
1. Parsing Arguments for Your Shell Script
2. Parsing Arguments with Your Own Error Messages
3. Parsing Some HTML
4. Parsing Output into an Array
5. Parsing Output with a Function Call
6. Parsing Text with a read Statement
7. Parsing with read into an Array
8. Getting Your Plurals Right
9. Taking It One Character at a Time
10. Cleaning Up an SVN Source Tree
11. Setting Up a Database with MySQL
12. Isolating Specific Fields in Data
13. Updating Specific Fields in Data Files
14. Trimming Whitespace
15. Compressing Whitespace
16. Processing Fixed-Length Records
17. Processing Files with No Line Breaks
18. Converting a Data File to CSV
19. Parsing a CSV Data File
Chapter 14 Writing Secure Shell Scripts
1. Avoiding Common Security Problems
2. Avoiding Interpreter Spoofing
3. Setting a Secure $PATH
4. Clearing All Aliases
5. Clearing the Command Hash
6. Preventing Core Dumps
7. Setting a Secure $IFS
8. Setting a Secure umask
9. Finding World-Writable Directories in Your $PATH
10. Adding the Current Directory to the $PATH
11. Using Secure Temporary Files
12. Validating Input
13. Setting Permissions
14. Leaking Passwords into the Process List
15. Writing setuid or setgid Scripts
16. Restricting Guest Users
17. Using chroot Jails
18. Running As a Non-root User
19. Using sudo More Securely
20. Using Passwords in Scripts
21. Using SSH Without a Password
22. Restricting SSH Commands
23. Disconnecting Inactive Sessions
Chapter 15 Advanced Scripting
1. Finding bash Portably for #!
2. Setting a POSIX $PATH
3. Developing Portable Shell Scripts
4. Testing Scripts in VMware
5. Using for Loops Portably
6. Using echo Portably
7. Splitting Output Only When Necessary
8. Viewing Output in Hex
9. Using bash Net-Redirection
10. Finding My IP Address
11. Getting Input from Another Machine
12. Redirecting Output for the Life of a Script
13. Working Around "argument list too long" Errors
14. Logging to syslog from Your Script
15. Sending Email from Your Script
16. Automating a Process Using Phases
Chapter 16 Configuring and Customizing bash
1. bash Startup Options
2. Customizing Your Prompt
3. Change Your $PATH Permanently
4. Change Your $PATH Temporarily
5. Setting Your $CDPATH
6. Shortening or Changing Command Names
7. Adjusting Shell Behavior and Environment
8. Adjusting readline Behavior Using .inputrc
9. Keeping a Private Stash of Utilities by Adding ~/bin
10. Using Secondary Prompts: $PS2, $PS3, $PS4
11. Synchronizing Shell History Between Sessions
12. Setting Shell History Options
13. Creating a Better cd Command
14. Creating and Changing into a New Directory in One Step
15. Getting to the Bottom of Things
16. Adding New Features to bash Using Loadable Built-ins
17. Improving Programmable Completion
18. Using Initialization Files Correctly
19. Creating Self-Contained, Portable RC Files
20. Getting Started with a Custom Configuration
Chapter 17 Housekeeping and Administrative Tasks
1. Renaming Many Files
2. Using GNU Texinfo and Info on Linux
3. Unzipping Many ZIP Files
4. Recovering Disconnected Sessions Using screen
5. Sharing a Single bash Session
6. Logging an Entire Session or Batch Job
7. Clearing the Screen When You Log Out
8. Capturing File Metadata for Recovery
9. Creating an Index of Many Files
10. Using diff and patch
11. Counting Differences in Files
12. Removing or Renaming Files Named with Special Characters
13. Prepending Data to a File
14. Editing a File in Place
15. Using sudo on a Group of Commands
16. Finding Lines in One File But Not in the Other
17. Keeping the Most Recent N Objects
18. Grepping ps Output Without Also Getting the grep Process Itself
19. Finding Out Whether a Process Is Running
20. Adding a Prefix or Suffix to Output
21. Numbering Lines
22. Writing Sequences
23. Emulating the DOS Pause Command
24. Commifying Numbers
Chapter 18 Working Faster by Typing Less
1. Moving Quickly Among Arbitrary Directories
2. Repeating the Last Command
3. Running Almost the Same Command
4. Substituting Across Word Boundaries
5. Reusing Arguments
6. Finishing Names for You
7. Playing It Safe
Chapter 19 Tips and Traps: Common Goofs for Novices
1. Forgetting to Set Execute Permissions
2. Fixing "No such file or directory" Errors
3. Forgetting That the Current Directory Is Not in the $PATH
4. Naming Your Script Test
5. Expecting to Change Exported Variables
6. Forgetting Quotes Leads to "command not found" on Assignments
7. Forgetting That Pattern Matching Alphabetizes
8. Forgetting That Pipelines Make Subshells
9. Making Your Terminal Sane Again
10. Deleting Files Using an Empty Variable
11. Seeing Odd Behavior from printf
12. Testing bash Script Syntax
13. Debugging Scripts
14. Avoiding "command not found" When Using Functions
15. Confusing Shell Wildcards and Regular Expressions

Appendix A Reference Lists
1. bash Invocation
2. Prompt String Customizations
3. ANSI Color Escape Sequences
4. Built-in Commands and Reserved Words
5. Built-in Shell Variables
6. set Options
7. shopt options
8. Adjusting Shell Behavior Using set, shopt, and Environment Variables
9. Test Operators
10. I/O Redirection
11. echo Options and Escape Sequences
12. printf
13. Date and Time String Formatting with strftime
14. Pattern-Matching Characters
15. extglob Extended Pattern-Matching Operators
16. tr Escape Sequences
17. Readline Init File Syntax
18. emacs Mode Commands
19. vi Control Mode Commands
20. Table of ASCII Values
Appendix B Examples Included with bash
1. Startup-Files Directory Examples
Appendix C Command-Line Processing
1. Command-Line Processing Steps
Appendix D Revision Control
1. CVS
2. Subversion
3. RCS
4. Other
Appendix E Building bash from Source
1. Obtaining bash
2. Unpacking the Archive
3. What's in the Archive
4. Who Do I Turn To?
Colophon

Return to bash Cookbook

Table of Contents

Chapter 1 Beginning bash

Why bash?

The bash Shell

Decoding the Prompt

Showing Where You Are

Finding and Running Commands

Getting Information About Files

Showing All Hidden (dot) Files in the Current Directory

Using Shell Quoting

Using or Replacing Built-ins and External Commands

Determining If You Are Running Interactively

Setting bash As Your Default Shell

Getting bash for Linux

Getting bash for xBSD

Getting bash for Mac OS X

Getting bash for Unix

Getting bash for Windows

Getting bash Without Getting bash

Learning More About bash Documentation

Chapter 2 Standard Output

Writing Output to the Terminal/Window

Writing Output but Preserving Spacing

Writing Output with More Formatting Control

Writing Output Without the Newline

Saving Output from a Command

Saving Output to Other Files

Saving Output from the ls Command

Sending Both Output and Error Messages to Different Files

Sending Both Output and Error Messages to the Same File

Appending Rather Than Clobbering Output

Using Just the Beginning or End of a File

Skipping a Header in a File

Throwing Output Away

Saving or Grouping Output from Several Commands

Connecting Two Programs by Using Output As Input

Saving a Copy of Output Even While Using It As Input

Connecting Two Programs by Using Output As Arguments

Using Multiple Redirects on One Line

Saving Output When Redirect Doesn't Seem to Work

Swapping STDERR and STDOUT

Keeping Files Safe from Accidental Overwriting

Clobbering a File on Purpose

Chapter 3 Standard Input

Getting Input from a File

Keeping Your Data with Your Script

Preventing Weird Behavior in a Here-Document

Indenting Here-Documents

Getting User Input

Getting Yes or No Input

Selecting from a List of Options

Prompting for a Password

Chapter 4 Executing Commands

Running Any Executable

Telling If a Command Succeeded or Not

Running Several Commands in Sequence

Running Several Commands All at Once

Deciding Whether a Command Succeeds

Using Fewer if Statements

Running Long Jobs Unattended

Displaying Error Messages When Failures Occur

Running Commands from a Variable

Running All Scripts in a Directory

Chapter 5 Basic Scripting: Shell Variables

Documenting Your Script

Embedding Documentation in Shell Scripts

Promoting Script Readability

Separating Variable Names from Surrounding Text

Exporting Variables

Seeing All Variable Values

Using Parameters in a Shell Script

Looping Over Arguments Passed to a Script

Handling Parameters with Blanks

Handling Lists of Parameters with Blanks

Counting Arguments

Consuming Arguments

Getting Default Values

Setting Default Values

Using null As a Valid Default Value

Using More Than Just a Constant String for Default