BASH Programming - Introduction HOW-TO

BASH Programming ? Introduction HOW?TO

BASH Programming ? Introduction HOW?TO

Table of Contents

BASH Programming ? Introduction HOW?TO.............................................................................................1

by Mike G mikkey at .ar.....................................................................................................1

1.Introduction...........................................................................................................................................1

2.Very simple Scripts...............................................................................................................................1

3.All about redirection.............................................................................................................................1

4.Pipes......................................................................................................................................................1

5.Variables...............................................................................................................................................2

6.Conditionals..........................................................................................................................................2

7.Loops for, while and until.....................................................................................................................2

8.Functions...............................................................................................................................................2

9.User interfaces......................................................................................................................................2

10.Misc....................................................................................................................................................2

11.Tables..................................................................................................................................................3

12.More Scripts........................................................................................................................................3

13.When something goes wrong (debugging).........................................................................................3

14.About the document............................................................................................................................3

1.Introduction...........................................................................................................................................3

1.1 Getting the latest version...................................................................................................................3

1.2 Requisites...........................................................................................................................................4

1.3 Uses of this document........................................................................................................................4

2.Very simple Scripts...............................................................................................................................4

2.1 Traditional hello world script.............................................................................................................4

2.2 A very simple backup script..............................................................................................................4

3.All about redirection.............................................................................................................................5

3.1 Theory and quick reference...............................................................................................................5

3.2 Sample: stdout 2 file .........................................................................................................................5

3.3 Sample: stderr 2 file ..........................................................................................................................5

3.4 Sample: stdout 2 stderr......................................................................................................................6

3.5 Sample: stderr 2 stdout .....................................................................................................................6

3.6 Sample: stderr and stdout 2 file ........................................................................................................6

4.Pipes......................................................................................................................................................6

4.1 What they are and why you'll want to use them................................................................................7

4.2 Sample: simple pipe with sed ...........................................................................................................7

4.3 Sample: an alternative to ls ?l *.txt ..................................................................................................7

5.Variables...............................................................................................................................................7

5.1 Sample: Hello World! using variables...............................................................................................7

5.2 Sample: A very simple backup script (little bit better)......................................................................8

5.3 Local variables...................................................................................................................................8

6.Conditionals..........................................................................................................................................9

6.1 Dry Theory.........................................................................................................................................9

6.2 Sample: Basic conditional example if .. then.....................................................................................9

6.3 Sample: Basic conditional example if .. then ... else.......................................................................10

6.4 Sample: Conditionals with variables...............................................................................................10

7.Loops for, while and until...................................................................................................................10

7.1 For sample........................................................................................................................................10

7.2 C?like for.........................................................................................................................................11

7.3 While sample...................................................................................................................................11

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BASH Programming ? Introduction HOW?TO

Table of Contents

7.4 Until sample.....................................................................................................................................11

8.Functions.............................................................................................................................................12

8.1 Functions sample.............................................................................................................................12

8.2 Functions with parameters sample...................................................................................................12

9.User interfaces....................................................................................................................................13

9.1 Using select to make simple menus.................................................................................................13

9.2 Using the command line .................................................................................................................13

10.Misc..................................................................................................................................................14

10.1 Reading user input with read.........................................................................................................14

10.2 Arithmetic evaluation.....................................................................................................................14

10.3 Finding bash ..................................................................................................................................15

10.4 Getting the return value of a program............................................................................................16

10.5 Capturing a commands output ......................................................................................................16

10.6 Multiple source files......................................................................................................................16

11.Tables................................................................................................................................................16

11.1 String comparison operators..........................................................................................................16

11.2 String comparison examples..........................................................................................................17

11.3 Arithmetic operators......................................................................................................................17

11.4 Arithmetic relational operators......................................................................................................18

11.5 Useful commands...........................................................................................................................18

12.More Scripts......................................................................................................................................22

12.1 Applying a command to all files in a directory.............................................................................22

12.2 Sample: A very simple backup script (little bit better)..................................................................22

12.3 File re?namer.................................................................................................................................23

12.4 File renamer (simple).....................................................................................................................24

13.When something goes wrong (debugging).......................................................................................25

13.1 Ways Calling BASH .....................................................................................................................25

14.About the document..........................................................................................................................25

14.1 (no) warranty..................................................................................................................................25

14.2 Translations....................................................................................................................................25

14.3 Thanks to........................................................................................................................................26

14.4 History...........................................................................................................................................26

14.5 More resources...............................................................................................................................26

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BASH Programming ? Introduction HOW?TO

by Mike G mikkey at .ar

Thu Jul 27 09:36:18 ART 2000

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 :)

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

BASH Programming ? Introduction HOW?TO

1

BASH Programming ? Introduction HOW?TO

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

5.Variables

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