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Mastering Bash

You're reading from   Mastering Bash A Step-by-Step Guide to working with Bash Programming and Shell Scripting

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Product type Paperback
Published in Jun 2017
Publisher Packt
ISBN-13 9781784396879
Length 502 pages
Edition 1st Edition
Languages
Tools
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Author (1):
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 Zarrelli Zarrelli
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Zarrelli
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Toc

Table of Contents (22) Chapters Close

Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
1. Let's Start Programming FREE CHAPTER 2. Operators 3. Testing 4. Quoting and Escaping 5. Menus, Arrays, and Functions 6. Iterations 7. Plug into the Real World 8. We Want to Chat 9. Subshells, Signals, and Job Controls 10. Lets Make a Process Chat 11. Living as a Daemon 12. Remote Connections over SSH 13. Its Time for a Timer 14. Time for Safety 1. Use in Real World Application

Exiting the loop with break and continue


This gives us nice opportunities, such as loops:

while true ; do echo "Hello" ; done

Since true always as true, the is always verified so we have an infinite execution of the do/done clause; press Ctrl+ C to exit from the loop. An infinite loop looks like something nasty, but it opens a new scenario for our scripts, since we can make them run or wait for something for as long as we want. Actually, if we do not use a couple of loop control commands: break will exit the loop and continue will restart it, jumping over the remaining commands. Let's see an example of creating a hypothetical backup program menu:

#!/bin/bash
while true
do
  clear
  cat <<MENU
  BACKUP UTIL v 1.0
  ------------------
  1. Backup a file/directory
  2. Restore a file/directory
  0. Quit
  ------------------
MENU
  read -p "Please select an option, 0 or Q to exit: " option
  case $option in
  1 | [Bb])
  echo "You chose the first option, Backup"
  sleep 3
  ;;
  2 | ...
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