bash Cookbook

Executing Commands
4.1. Running Any Executable
4.2. Running Several Commands in Sequence
4.3. Running Several Commands All at Once
4.4. Telling Whether a Command Succeeded or Not
4.5. Running a Command Only if Another Command Succeeded
4.6. Using Fewer if Statements
4.7. Running Long Jobs Unattended
4.8. Displaying Error Messages When Failures Occur
4.9. Running Commands from a Variable
4.10. Running All Scripts in a Directory

Basic Scripting: Shell Variables
5.1. Documenting Your Script
5.2. Embedding Documentation in Shell Scripts
5.3. Promoting Script Readability
5.4. Separating Variable Names from Surrounding Text
5.5. Exporting Variables
5.6. Seeing All Variable Values
5.7. Using Parameters in a Shell Script
5.8. Looping Over Arguments Passed to a Script
5.9. Handling Parameters with Spaces
5.10. Handling Lists of Parameters with Spaces
5.11. Counting Arguments
5.12. Consuming Arguments
5.13. Getting Default Values
5.14. Setting Default Values
5.15. Using null as a Valid Default Value
5.16. Using More than Just a Constant String for Default
5.17. Giving an Error Message for Unset Parameters
5.18. Changing Pieces of a String
5.19. Getting the Absolute Value of a Number
5.20. Using bash for basename
5.21. Using bash for dirname
5.22. Using Alternate Values for Comma Separated Values
5.23. Using Array Variables
5.24. Converting Between Upper- and Lowercase
5.25. Converting to Camel Case

Shell Logic and Arithmetic
6.1. Doing Arithmetic in Your Shell Script
6.2. Branching on Conditions
6.3. Testing for File Characteristics
6.4. Testing for More than One Thing
6.5. Testing for String Characteristics
6.6. Testing for Equality
6.7. Testing with Pattern Matches
6.8. Testing with Regular Expressions
6.9. Changing Behavior with Redirections
6.10. Looping for a While
6.11. Looping with a read
6.12. Looping with a Count
6.13. Looping with Floating-Point Values
6.14. Branching Many Ways
6.15. Parsing Command-Line Arguments
6.16. Creating Simple Menus
6.17. Changing the Prompt on Simple Menus
6.18. Creating a Simple RPN Calculator
6.19. Creating a Command-Line Calculator

Intermediate Shell Tools I
7.1. Sifting Through Files for a String
7.2. Getting Just the Filename from a Search
7.3. Getting a Simple True/False from a Search
7.4. Searching for Text While Ignoring Case
7.5. Doing a Search in a Pipeline
7.6. Paring Down What the Search Finds
7.7. Searching with More Complex Patterns
7.8. Searching for an SSN
7.9. Grepping Compressed Files
7.10. Keeping Some Output, Discarding the Rest
7.11. Keeping Only a Portion of a Line of Output
7.12. Reversing the Words on Each Line
7.13. Summing a List of Numbers
7.14. Counting String Values with awk
7.15. Counting String Values with bash
7.16. Showing Data as a Quick and Easy Histogram
7.17. An Easy Histogram with bash
7.18. Showing a Paragraph of Text After a Found Phrase

Intermediate Shell Tools II
8.1. Sorting Your Output
8.2. Sorting Numbers
8.3. Sorting IP Addresses
8.4. Cutting Out Parts of Your Output
8.5. Removing Duplicate Lines
8.6. Compressing Files
8.7. Uncompressing Files
8.8. Checking a tar Archive for Unique Directories
8.9. Translating Characters
8.10. Converting Uppercase to Lowercase
8.11. Converting DOS Files to Linux Format
8.12. Removing Smart Quotes
8.13. Counting Lines, Words, or Characters in a File
8.14. Rewrapping Paragraphs
8.15. Doing More with less

Finding Files: find, locate, slocate
9.1. Finding All Your MP3 Files
9.2. Handling Filenames Containing Odd Characters
9.3. Speeding Up Operations on Found Files
9.4. Finding Files Across Symbolic Links
9.5. Finding Files Irrespective of Case
9.6. Finding Files by Date
9.7. Finding Files by Type
9.8. Finding Files by Size
9.9. Finding Files by Content
9.10. Finding Existing Files and Content Fast
9.11. Finding a File Using a List of Possible Locations

Additional Features for Scripting
10.1. “Daemon-izing” Your Script
10.2. Reusing Code with Includes and Sourcing
10.3. Using Configuration Files in a Script
10.4. Defining Functions
10.5. Using Functions: Parameters and Return Values
10.6. Trapping Interrupts
10.7. Redefining Commands with alias
10.8. Avoiding Aliases and Functions
10.9. Counting Elapsed Time
10.10. Writing Wrappers

Working with Dates and Times
11.1. Formatting Dates for Display
11.2. Supplying a Default Date
11.3. Automating Date Ranges
11.4. Converting Dates and Times to Epoch Seconds
11.5. Converting Epoch Seconds to Dates and Times
11.6. Getting Yesterday or Tomorrow with Perl
11.7. Figuring Out Date and Time Arithmetic
11.8. Handling Time Zones, Daylight Saving Time, and Leap Years
11.9. Using date and cron to Run a Script on the Nth Day
11.10. Logging with Dates

End-User Tasks as Shell Scripts
12.1. Starting Simple by Printing Dashes
12.2. Viewing Photos in an Album
12.3. Loading Your MP3 Player
12.4. Burning a CD
12.5. Comparing Two Documents

Parsing and Similar Tasks
13.1. Parsing Arguments for Your Shell Script
13.2. Parsing Arguments with Your Own Error Messages
13.3. Parsing Some HTML
13.4. Parsing Output into an Array
13.5. Parsing Output with a Function Call
13.6. Parsing Text with a read Statement
13.7. Parsing with read into an Array
13.8. Reading an Entire File
13.9. Getting Your Plurals Right
13.10. Taking It One Character at a Time
13.11. Cleaning Up an SVN Source Tree
13.12. Setting Up a Database with MySQL
13.13. Isolating Specific Fields in Data
13.14. Updating Specific Fields in Datafiles
13.15. Trimming Whitespace
13.16. Compressing Whitespace
13.17. Processing Fixed-Length Records
13.18. Processing Files with No Line Breaks
13.19. Converting a Datafile to CSV
13.20. Parsing a CSV Datafile

Writing Secure Shell Scripts
14.1. Avoiding Common Security Problems
14.2. Avoiding Interpreter Spoofing
14.3. Setting a Secure $PATH
14.4. Clearing All Aliases
14.5. Clearing the Command Hash
14.6. Preventing Core Dumps
14.7. Setting a Secure $IFS
14.8. Setting a Secure umask
14.9. Finding World-Writable Directories in Your $PATH
14.10. Adding the Current Directory to the $PATH
14.11. Using Secure Temporary Files
14.12. Validating Input
14.13. Setting Permissions
14.14. Leaking Passwords into the Process List
14.15. Writing setuid or setgid Scripts
14.16. Restricting Guest Users
14.17. Using chroot Jails
14.18. Running as a Non-root User
14.19. Using sudo More Securely
14.20. Using Passwords in Scripts
14.21. Using SSH Without a Password
14.22. Restricting SSH Commands
14.23. Disconnecting Inactive Sessions

Advanced Scripting
15.1. Finding bash Portably for #!
15.2. Setting a POSIX $PATH
15.3. Developing Portable Shell Scripts
15.4. Testing Scripts Using Virtual Machines
15.5. Using for Loops Portably
15.6. Using echo Portably
15.7. Splitting Output Only When Necessary
15.8. Viewing Output in Hex
15.9. Using bash Net-Redirection
15.10. Finding My IP Address
15.11. Getting Input from Another Machine
15.12. Redirecting Output for the Life of a Script
15.13. Working Around “Argument list too long” Errors
15.14. Logging to syslog from Your Script
15.15. Using logger Correctly
15.16. Sending Email from Your Script
15.17. Automating a Process Using Phases
15.18. Doing Two Things at Once
15.19. Running an SSH command on multiple hosts

Configuring and Customizing bash
16.1. bash Startup Options
16.2. Customizing Your Prompt
16.3. A Prompt Before Your Program Runs
16.4. Changing Your $PATH Permanently
16.5. Changing Your $PATH Temporarily
16.6. Setting Your $CDPATH
16.7. When Programs Are Not Found
16.8. Shortening or Changing Command Names
16.9. Adjusting Shell Behavior and Environment
16.10. Adjusting readline Behavior Using .inputrc
16.11. Keeping a Private Stash of Utilities by Adding ~/bin
16.12. Using Secondary Prompts: $PS2, $PS3, $PS4
16.13. Synchronizing Shell History Between Sessions
16.14. Setting Shell History Options
16.15. Creating a Better cd Command
16.16. Creating and Changing Into a New Directory in One Step
16.17. Getting to the Bottom of Things
16.18. Adding New Features to bash Using Loadable Builtins
16.19. Improving Programmable Completion
16.20. Using Initialization Files Correctly
16.21. Creating Self-Contained, Portable rc Files
16.22. Getting Started with a Custom Configuration

Housekeeping and Administrative Tasks
17.1. Renaming Many Files
17.2. Using GNU Texinfo and info on Linux
17.3. Unzipping Many ZIP Files
17.4. Recovering Disconnected Sessions Using screen
17.5. Sharing a Single bash Session
17.6. Logging an Entire Session or Batch Job
17.7. Clearing the Screen When You Log Out
17.8. Capturing File Metadata for Recovery
17.9. Creating an Index of Many Files
17.10. Using diff and patch
17.11. Counting Differences in Files
17.12. Removing or Renaming Files Named with Special Characters
17.13. Prepending Data to a File
17.14. Editing a File in Place
17.15. Using sudo on a Group of Commands
17.16. Finding Lines That Appear in One File but Not in Another
17.17. Keeping the Most Recent N Objects
17.18. Writing to a Circular Log
17.19. Circular Backups
17.20. Grepping ps Output Without Also Getting the grep Process Itself
17.21. Finding Out Whether a Process Is Running
17.22. Adding a Prefix or Suffix to Output
17.23. Numbering Lines
17.24. Writing Sequences
17.25. Emulating the DOS Pause Command
17.26. Commifying Numbers

Working Faster by Typing Less
18.1. Moving Quickly Among Arbitrary Directories
18.2. Repeating the Last Command
18.3. Running Almost the Same Command
18.4. Quick Substitution
18.5. Reusing Arguments
18.6. Finishing Names for You
18.7. Playing It Safe
18.8. Big Changes, More Lines

Tips and Traps: Common Goofs for Novices
19.1. Forgetting to Set Execute Permissions
19.2. Fixing “No such file or directory” Errors
19.3. Forgetting That the Current Directory Is Not in the $PATH
19.4. Naming Your Script “test”
19.5. Expecting to Change Exported Variables
19.6. Forgetting Quotes Leads to “command not found” on Assignments
19.7. Forgetting that Pattern Matching Alphabetizes
19.8. Forgetting that Pipelines Make Subshells
19.9. Making Your Terminal Sane Again
19.10. Deleting Files Using an Empty Variable
19.11. Seeing Odd Behavior from printf
19.12. Testing bash Script Syntax
19.13. Debugging Scripts
19.14. Avoiding “command not found” When Using Functions
19.15. Confusing Shell Wildcards and Regular Expressions

Reference Lists
bash Invocation
Prompt String Customizations
ANSI Color Escape Sequences
Builtin Commands
bash Reserved Words
Builtin Shell Variables
set Options
shopt Options
Test Operators
I/O Redirection
echo Options and Escape Sequences
printf
Date and Time String Formatting with strftime
Pattern-Matching Characters
extglob Extended Pattern-Matching Operators
tr Escape Sequences
readline Init File Syntax
Table of ASCII Values
Examples Included with bash
bash Documentation and Examples
Command-Line Processing
Command-Line Processing Steps
Revision Control
Git
Bazaar
Mercurial
Subversion
Meld
etckeeper
Other
Building bash from Source
Obtaining bash
Unpacking the Archive
What’s in the Archive
Who Do I Turn To?

Index