Lab 3 - Bash Scripting

In this lab, we will explore the basics of bash scripting by creating several simple but fundamental scripts that demonstrate essential programming concepts. Through these exercises, you will learn how to write a "hello world" script, interact with users via input, and perform conditional operations like checking if a number is even or odd. Additionally, we will practice file manipulation by creating a script to search for a specific string within a file. Lastly, we will tackle a more advanced assignment—building a phonebook script to manage and search contact information. These tasks will lay the foundation for understanding how to write practical and efficient shell scripts to automate processes and manage data.

Objectives

1. Read through the following link up to the "Script Lab Assignment Section" [Berkely.edu]
2. Create a "Hello World" bash script
3. Create a bash script capable of receiving user input
4. Create a bash script to show if a number is even or odd
5. Create a bash script that checks a given file for a string and prints true if found
6. Complete the phonebook assignment as dictated in the above

Initial Setup

You should create a directory in your home path called “scripts”. Don’t forget to run the chmod +x filename command on these scripts to make them executable. Be sure to name the file the specified filename.

You do not have to create these scripts with in your VM. Instead, developing them on your personal device using WSL (If on Windows) or directly on MacOS is perfectly fine.

Hello World

Filename: helloworld
Example: ./helloworld

Create a bash script that prints "Hello World!" when executed.

Demonstrate User Input

Filename: userinput
Example: ./userinput
Create a bash script capable of taking user input. This script should prompt the user for their age, then when given print out a statement saying "The user is X years old". If you would like, you can leverage loops to make it ask continuously.

Even or Odd

Filename: iseven
Example: ./iseven 12

Write a bash script that takes a number as an argument. Finally, it should print out whether the number is even or odd.

String Search

Filename: filecontains
Example: ./filecontains /path/to/file searchstring

Create a bash script that takes the pathname of a text file as an argument, and then a string to search for. The script should then check the specified file for that string and print out whether or not it was found. As a bonus, print out the line number(s) the string was found on.

Phonebook Assignment

Filename: phonebook
Visit this link. At the end, there is a section labeled "Scripting Lab Assignment". Your phonebook script should be able to do all the following:

• Create a new entry
  • $ ./phonebook new "Linus Torvalds" 101-110-0111
• List all entries
  • $ ./phonebook list
  • > Linus Torvalds 101-110-1010
• Lookup and entry
  • $ ./phonebook lookup "Linus Torvalds"
  • > 101-110-0111
  • If the same name has multiple phone numbers, it should print all of them out
• Remove an entry
  • $ ./phonebook remove "Linus Torvalds"
  • > 1 record(s) deleted
    

Notes on the phonebook assignment:

• You will need a method to persistently store entries between execution
  • A text file is the easiest method, but feel free to use whatever method you like
  • Investigate sqlite for a different solution
• Aim for simplicity and look for commands which already exist in your system which you can use in your script to help simplify your work
• Approach the script in bite-sized chunks, focusing on getting individual pieces to function properly
• Read up on piping in bash, as this script will benefit from it's use
• Please ensure that your outputs look similar to the expected outputs listed above

Deliverables

• Demonstrate all five of the bash scripts functioning as specified to me
• Submit them all in a ZIP file to the lab drop box on eClass