Ruby SQLite Tutorial

SQLite3 is an awesome cross-platform relational database. Some of the major benefits of SQLite include its simplicity and easy management. Everything is stored in a single file and there is no authentication.

One of the big drawbacks with a SQLite database is that there is a global write-lock. Only one write operation can occur at any time. This can create a bottleneck for very write-intensive applications.

SQLite is used in production in many embedded and web applications. For example, you can use SQLite in combination with the Sinatra web application framework to persist data. If you are interested in learning how to use Sinatra, check out my Sinatra Tutorial.

Ruby is an incredibly productive and useful language. Combining Ruby with SQLite3 is a natural fit that opens many possibilities. Add in a simple web framework like Sinatra and you have an incredibly powerful but simple set of tools for building a web application.

You can read more on the official SQLite3 website and on the SQLite Wikipedia article.

If you need a database-agnostic library, something that you can use with SQLite and then easily configure to start using MySQL without rewriting all of your code, you want to use an ORM. ORM stands for Object-Relational-Mapping and the most popular one for Ruby is ActiveRecord.

Ruby Sinatra Tutorial

Sinatra is a minimalist web framework for the Ruby programming language. It is known for being very simple and easy to use. If you are familiar with express.js, it was inspired by Sinatra. I have found it to be incredibly useful and fast to work with. This tutorial will cover some of the common tasks that I have used.

Deploy Ruby Rack Web Apps with uWSGI and Nginx

This tutorial demonstrates how to deploy a Ruby web app using the Sinatra framework using uWSGI and nginx as the web server. This uses the config.ru standard for creating a web app. You can use this method to work with several other Ruby web frameworks including Rails.

This was tested on Fedora 30. Slight modification might be needed for other distributions.

How to Verify a Checksum

A checksum is a special type of hash that is used to verify the integrity of a file. Verifying a checksum ensures there was no corruption or manipulation during the download and the file was downloaded completely and correctly.

A common use case for checksum verification is to verify a large download like an .iso disk image. MD5 and SHA1 hashes are commonly used for this task. We will look at easy ways to obtain a hash to verify a checksum.

How to Verify a GPG Signature

This tutorial covers the process of verifying a GPG signature, which is commonly done to verify the authenticity of a email, document, or downloaded file to ensure it came from the expected source. This only covers verifying signature and not creating them. To learn how to sign and how to sign-and-encrypt, read GPG Tutorial - Signatures.

GPG offers a lot more functionality than just verifying signatures though. To learn more about GPG in general and how to manage keys, encrypt, sign, and more, read my GPG Tutorial.

Curses Programming in Python

The curses and ncurses (new curses) libraries go back to 1980's and 90's and provide an API to create textual user interfaces (TUI). If you write a command-line application, you should consider using curses to implement functionality you could not otherwise do with standard console output. The text editor nano is a good example of a ncurses application. We will look at how to use this library in Python.

Python3 Qt5 (PyQt5) Tutorial

Qt is a robust cross-platform framework that works on Windows, Linux, Mac, Android, and more. It allows you to create GUI applications as well as provides libraries for networking,

In this tutorial, we will focus on some of the very core aspects of using PyQt5 and how to package it for distribution.

Here is an example project I created using Pyqt5: https://github.com/DevDungeon/PyQt5-Bitcoin-Price-Checker and the live coding of that project https://www.devdungeon.com/content/live-coding-pyqt5-guis-w-python.

PyInstaller Tutorial

PyInstaller can be used to create .exe files for Windows, .app files for Mac, and distributable packages for Linux. Optionally, it can create a single file which is more convenient for distributing, but takes slightly longer to start because it unzip itself.

This tutorial walks through the process of installing and using PyInstaller to create distributable packages.

VirtualBox Disk Encryption Tutorial

VirtualBox allows you to encrypt the virtual disk files at the VM level. This means you can use VirtualBox to encrypt the disks even if the operating system you are installing does not support disk encryption or you simply prefer not to use something like LVM disk encryption. One benefit of doing this is that you can still use dynamically expanding disks. If you choose an encrypted LVM disk, you can end up with the maximum size of the virtual disk being used which is highly inefficient for disk space.

Enhanced Shell Scripting with Ruby

Ruby is a better Perl and in my opinion is an essential language for system administrators. If you are still writing scripts in Bash, I hope this inspires you to start integrating Ruby in to your shell scripts. I will show you how you can ease in to it and make the transition very smoothly.

The idea with 'enhanced shell scripting' is to create hybrid Ruby/Bash scripts. The reason for this is to take advantage of both worlds. Ruby makes it seamless to pass data back and forth with shell commands.

There are many times when running shell commands is easier or required when there is an external command-line utilities you need to run.

On the other hand, Bash syntax is quite ugly and difficult to remember, and it has very limited features. Ruby offers two tons of object-oriented power, along with tons of libraries and better syntax.

We will look at how to write 'enhanced shell scripts' using Ruby and other tips on taking advantage of both worlds.

How to solve "Error: Cannot find module '*.js'" with Node.js

If you are trying to run your Node.js application and you get something like this:

Error: Cannot find module 'C:\Users\Me\my_app.js'

then you are most likely trying to run the wrong file. It is possible you are missing a dependency that is needed from npm install, but if it says it cannot find the main file you are trying to run, then you are trying to run a file that does not exist. It is a common mistake.