Introduction

Conditional statements are indispensable to any useful scripting and full-featured programming language. On the third part of our Shell Script tutorial, you’ll learn all the “if’s” and “else’s” of bash, and how to use them to your advantage. This article has also been written assuming you have already configured your shell script folder according to the first tutorial.

The “if” command

A conditional statement is used to perform certain actions if a condition is true or false. With shell scripts, this is performed by the “if” command. It’s followed by an expression that’s going to be tested. This expression can also be the exit code of the execution of a command, a mathematical expression, beyond other various things. When working with exit codes, the command is pretty straightforward:

if ls folder
then
echo "Folder exists"
fi

If the folder exists, the echo command will run, because ls will have returned exit code 0, as in successful. Otherwise, if the folder doesn’t exist, the text will not be displayed. All “if” statements need to be followed by the “then” command, and ended with “fi”. If you’re not working with exit codes, and want to test a mathematical expression for example, you’ll need the “test” command. There are the following operators in shell script to compare numbers: Continue reading How To Write a Simple Shell Script on a VPS (Part 3) →

Introduction

The second part of this tutorial will teach you more basic commands for shell scripts on a VPS. They are responsible for both displaying and gathering information to and from the user. This article has been written assuming you have already configured your shell script folder according to the first tutorial.

The echo Command

This command enables you to display information for the user. You can display simple text strings, variables, or both of them together. It has two parameters: -n, which makes the text displayed not be followed by a new line, and -e, which enables the following set of “code” inside the string:

\a   - Alert sound
\b   - Backspace character
\c   - Don’t display new line
\e   - Escape character
\n   - New line
\r   - Carriage return
\t   - Horizontal tab
\0xx - ASCII character
\\   - Backslash

For example, the following commands perform exactly the same: Continue reading How To Write a Simple Shell Script on a VPS (Part 2) →

Introduction

This tutorial is aimed at teaching you how to write shell scripts for the most variety of purposes. Shell scripts can be used to run multiple commands, a single command with difficult and extensive arguments, or more user friendly interfaces for distributing your work. Essentially it makes your life easier by automating stuff you’d have to do manually without it.

Setting Up a Folder

Before you start writing your shell script, it’s a good practice to designate it a folder. It’s recommended that, for personal scripts, you do it over at ~/bin. To create that folder, run: Continue reading How To Write a Simple Shell Script on a VPS →