Bash-Beginners-Guide

Bash Guide for Beginners
Table of Contents
Introduction.........................................................................................................................................................1
1. Why this guide?...................................................................................................................................1
2. Who should read this book?.................................................................................................................1
3. New versions, translations and availability.........................................................................................2
4. Revision History..................................................................................................................................2
5. Contributions.......................................................................................................................................3
6. Feedback..............................................................................................................................................3
7. Copyright information.........................................................................................................................3
8. What do you need?...............................................................................................................................4
9. Conventions used in this document.....................................................................................................4
10. Organization of this document...........................................................................................................5
Chapter 1. Bash and Bash scripts......................................................................................................................6
1.1. Common shell programs...................................................................................................................6
1.1.1. General shell functions............................................................................................................6
1.1.2. Shell types...............................................................................................................................6
1.2. Advantages of the Bourne Again SHell............................................................................................7
1.2.1. Bash is the GNU shell.............................................................................................................7
1.2.2. Features only found in bash.....................................................................................................7
1.3. Executing commands......................................................................................................................12
1.3.1. General..................................................................................................................................12
1.3.2. Shell built-in commands........................................................................................................12
1.3.3. Executing programs from a script.........................................................................................13
1.4. Building blocks...............................................................................................................................13
1.4.1. Shell building blocks.............................................................................................................13
1.5. Developing good scripts.................................................................................................................15
1.5.1. Properties of good scripts......................................................................................................16
1.5.2. Structure................................................................................................................................16
1.5.3. Terminology..........................................................................................................................16
1.5.4. A word on order and logic.....................................................................................................16
1.5.5. An example Bash script: mysystem.sh..................................................................................17
1.5.6. Example init script.................................................................................................................18
1.6. Summary.........................................................................................................................................19
1.7. Exercises.........................................................................................................................................19
Chapter 2. Writing and debugging scripts.....................................................................................................21
2.1. Creating and running a script..........................................................................................................21
2.1.1. Writing and naming...............................................................................................................21
2.1.2. script1.sh................................................................................................................................22
2.1.3. Executing the script...............................................................................................................23
2.2. Script basics....................................................................................................................................24
2.2.1. Which shell will run the script?.............................................................................................24
2.2.2. Adding comments..................................................................................................................24
2.3. Debugging Bash scripts..................................................................................................................25
2.3.1. Debugging on the entire script..............................................................................................25
2.3.2. Debugging on part(s) of the script.........................................................................................26
2.4. Summary.........................................................................................................................................28
2.5. Exercises.........................................................................................................................................28
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