BASH Programming - Introduction HOW-TO

by Mike G mikkey at dynamo.com.ar

Thu Jul 27 09:36:18 ART 2000

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This article intends to help you to start programming basic-intermediate shell scripts. It does not intend to be an advanced document (see the title). I am NOT an expert nor guru shell programmer. I decided to write this because I'll learn a lot and it might be useful to other people. Any feedback will be apreciated, specially in the patch form :)

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1. Introduction

• 1.1 Getting the latest version
• 1.2 Requisites
• 1.3 Uses of this document

2. Very simple Scripts

• 2.1 Traditional hello world script
• 2.2 A very simple backup script

3. All about redirection

• 3.1 Theory and quick reference
• 3.2 Sample: stdout 2 file
• 3.3 Sample: stderr 2 file
• 3.4 Sample: stdout 2 stderr
• 3.5 Sample: stderr 2 stdout
• 3.6 Sample: stderr and stdout 2 file

4. Pipes

• 4.1 What they are and why you'll want to use them
• 4.2 Sample: simple pipe with sed
• 4.3 Sample: an alternative to ls -l *.txt

5. Variables

• 5.1 Sample: Hello World! using variables
• 5.2 Sample: A very simple backup script (little bit better)
• 5.3 Local variables

6. Conditionals

• 6.1 Dry Theory
• 6.2 Sample: Basic conditional example if .. then
• 6.3 Sample: Basic conditional example if .. then ... else
• 6.4 Sample: Conditionals with variables

7. Loops for, while and until

• 7.1 For sample
• 7.2 C-like for
• 7.3 While sample
• 7.4 Until sample

8. Functions

• 8.1 Functions sample
• 8.2 Functions with parameters sample

9. User interfaces

• 9.1 Using select to make simple menus
• 9.2 Using the command line

10. Misc

• 10.1 Reading user input with read
• 10.2 Arithmetic evaluation
• 10.3 Finding bash
• 10.4 Getting the return value of a program
• 10.5 Capturing a commands output
• 10.6 Multiple source files

11. Tables

• 11.1 String comparison operators
• 11.2 String comparison examples
• 11.3 Arithmetic operators
• 11.4 Arithmetic relational operators
• 11.5 Useful commands

12. More Scripts

• 12.1 Applying a command to all files in a directory.
• 12.2 Sample: A very simple backup script (little bit better)
• 12.3 File re-namer
• 12.4 File renamer (simple)

13. When something goes wrong (debugging)

• 13.1 Ways Calling BASH

14. About the document

• 14.1 (no) warranty
• 14.2 Translations
• 14.3 Thanks to
• 14.4 History
• 14.5 More resources