Book Image

Mastering Linux Shell Scripting

By : Andrew Mallett
Book Image

Mastering Linux Shell Scripting

By: Andrew Mallett

Overview of this book

Shell scripting is a quick method to prototype a complex application or a problem by automating tasks when working on Linux-based systems. Using both simple one-line commands and command sequences complex problems can be solved with ease, from text processing to backing up sysadmin tools. In this book, you’ll discover everything you need to know to master shell scripting and make informed choices about the elements you employ. Get to grips with the fundamentals of creating and running a script in normal mode, and in debug mode. Learn about various conditional statements' code snippets, and realize the power of repetition and loops in your shell script. Implement functions and edit files using the Stream Editor, script in Perl, program in Python – as well as complete coverage of other scripting languages to ensure you can choose the best tool for your project.
Table of Contents (21 chapters)
Mastering Linux Shell Scripting
About the Author
About the Reviewer

Using functions in menus

In the last chapter, Chapter 6, Iterating with Loops we created the file. Menus are great targets to use functions, as the case statement is maintained very simply with single line entries, while the complexity can still be stored in each function. We should consider creating a function for each menu item. If we copy the previous $HOME/bin/ to $HOME/bin/, we can improve the functionality. The new menu should look like the following code:

# Author: @theurbanpenguin
# Web:
# Sample menu with functions
# Last Edited: Sept 2015

function to_lower {
    output=$(tr [A-Z] [a-z] <<< "$input")
return $output

function do_backup {
    tar -czvf $HOME/backup.tgz ${HOME}/bin

function show_cal {
    if [ -x /usr/bin/ncal ] ; then
      command="/usr/bin/ncal -w"

while true
  echo "Choose an item: a, b or c"
  echo "a: Backup...