Cli-Tools

If you grind old Advent of Code problems, you might notice a particular style of problem crop up more than once. The people of Reddit refer to their solutions as a variation of Conway’s Game of Life (GoL). Wikipedia has a great article on GoL. The animations are eye catching. The Wiki serves as motivation for a terminal app that visualizes GoL simulations. Rules of the Game What are the GoL rules? The setup is simple. You have an MxN grid of “cells.” Each cell is always in one of two states: live or dead. The grid transitions through states on a frame tick. You apply the following rule at each tick. ...

You ever come across one of those ASMR programming videos? This video where the developer programs a terminal display with a couple of spinning cubes is neat. This video is the motivation for the development of a ncurses application that renders a user controlled 3D cube. Perspective Projection and Rotation Matrices So how do you take an object in 3D space and visualize it in 2D space? The answer is perspective projection. Many videos explain the technique in detail. One of the better videos is “Carl the Person”’s (cool name by the way) video tutorial: ...

If you’re familiar with the kbhell application, you might realize that kbhell is about 90% of the way to being a keylogger. Why not finish the job and write a proper, cross platform keylogger that captures a victim’s every keystroke (for science reasons, of course)? The Requirements So there’s the obvious requirement of capturing user keystrokes. When you think about the fact that keyboards have different layouts, there are different language sets, etc., the task becomes challenging. ...

Do you enjoy the sound of a mechanical keyboard? What if it was possible to achieve the sound of the keys clacking without having an actual mechanical keyboard? That was the idea that spawned this keyboard hell (kbhell) project. That and trolling friends by playing a soundbite every time they press a key! Getting Started When a user performs any keystroke, a audio file gets played. One of the main kbhell requirements is that it runs on both Windows and Linux. That leaves you with two problems to solve: ...

While on a LeetCode grind, I came across a fun problem involving Morse code: Unique Morse Code Words. You might wonder what the encodings sound like. With a little programming magic you can find out by creating a command line utility for converting text to Morse code audio. The Basics The journey starts at the Morse code wiki page. The wiki had a chart that sums up the protocol: The chart though labeled “International Morse Code” seems basic. Where are all the accents and punctuations? Turns out there’s an organization, International Telecommunication Union, which has documents defining the complete set of supported characters. ...

Most programmers young and old have seen the cyberpunk sci-fi film The Matrix. One of the most outstanding parts of the movie is the closing scene where Neo sees the Matrix when battling the Agents: The visual effect with the code running along all the surfaces is iconic. Seems other people thought so too to the point that the effect has a name: Matrix Digital Rain. Wouldn’t it be neat to create a terminal screensaver that mimicked the effect seen in the movie? ...

When debugging an embedded system, it’s common to work with raw data requiring conversion between decimal, hexadecimal, binary, and sometimes octal number systems. The Python REPL and printf shell utility do the job but are tedious to use for the simple task of base conversion. It would be nice to drop the overhead of format specifiers and fear of numerical limits. To ease the pain, I decided to write a command line utility that made conversion between positive binary, decimal, octal, and hexadecimal numbers of arbitrary size. ...

Implementing a Huffman Tree is a fun afternoon project for anyone interested in learning about data compression. A Huffman Tree is a type of binary tree that sees use in the compression of an arbitrary data file. Developing a command line utility to compress/decompress a file using Huffman coding is a good CS101 challenge. Breaking It Down Into Steps This project starts where many do: Wikipedia. The Huffman Coding wiki article gives a nice breakdown with examples of the data structure and associated algorithms. In particular, the “Basic Technique” section covers the algorithms for compression and decompression. You need three key data structures to implement the big Compress() and Decompress() routines: ...

There’s a neat Computerphile video discussing the topic of steganography. In the video, Mike Pound talks about a technique for steganography on digital images: least significant bit substitution (LSBS). The effectiveness of LSBS in concealing a secret image is surprising. This article puts least significant bit substitution to use in a command line tool for embedding one image within another. A Little Background on Digital Images You don’t need fancy image manipulation techniques to make this steganography tool work. That said, you do need to know a little bit about how the machine represents a digital image. ...

Are you a text user interface enjoyer? Have you always wondered how difficult is it to write an ncurses UI? What better way to find out than to write a program of your own that explores ncurses’ API. Of course, you have to keep it interesting. Why not implement a scaled down version of a retro arcade game: snake. The Rules of Snake Step one of this project is to look up what the rules for a game of snake are. Specifically, what does the play “arena” look like, how do you win, and how do you lose? ...