code

53 Articles

Blowing Up Shell Scripts

September 18, 2024 by 24 Comments

One of the most universal experiences of any Linux or Unix user is working through a guide or handbook and coming across an almost unbelievably complex line of code meant to be executed with a shell. At the time of encountering a snippet like this it’s difficult to imagine any human ever having written it in the first place, but with some dedication it is possible to tease out what these small bits of code do when they’re typed into the terminal and run (unless it’s something like :(){ :|:& };: but that’s another story entirely). [noperator] recently built a tool which helps users in this predicament understand these shell scripts by expanding them into a more human-intelligible form.

The tool is named sol and does much more than expanding shell one-liners into a readable format. It also provides an interactive shell environment where the user can explore the exploded code in detail, modify it in any way they see fit, and collapse it back down to a single line so it can easily be sent to other users. It can be used with most of the major text editors as well as piped directly to standard input, and has a number of other options as well such as custom configurations and the ability to see non-standard bits of code that might not be compatible from one shell environment to another, as well as helping to translate those bits of code.

[noperator] has made the code available in the linked GitHub page for anyone curious about its use, and has a to-do list for future versions of the tool as well including adding support beyond bash. We’d definitely recommend a tool like this especially if you’re still relatively new to bash scripting (or shell scripting in general) and, as always, we’d just to remind everyone not to blindly copy and paste commands into their terminal windows. If you’re the type of person to go out on a limb and run crazy commands to see what they actually do, though, make sure you’re at least logged into the right computer first.

Compiling Four Billion If Statements

August 7, 2024 by 44 Comments

With modern tools, you have to try very hard to do something stupid, because the tools (rightly) recognize you’re doing something stupid. [Andreas Karlsson] can speak to that first hand as he tried to get four billion if statements to compile.

You may ask what state space requires four billion comparisons to evaluate? The answer is easy: the range of an unsigned 32-bit integer. The whole endeavor started with a simple idea: what if instead of evaluating whether an integer is even or odd with a modulo or bit mask, you just did an if statement for every case? Small ranges like 0-10 are trivial to write out by hand, but you reach for more automated solutions as you pass 8 bits and move towards 16. [Andreas] wrote some Python that outputs a valid C program with all the comparisons. For 16 bits, the source only clocks in at 130k lines with the executable less than 2 MB.

Of course, scaling to 32 bits is a very different problem. The source file balloons to 330 GB, and most compilers barf at that point. Undeterred, [Andreas] modified the Python to output x86_64 assembly instead of C. Of course, the executable format of Windows (PE) only allows executables up to 4 GB, so a helper program mapped the 40 GB generated executable and jumped into it.

What’s incredible about this whole journey is how performant the program is. Even large numbers complete in a few seconds. Considering that it has to thrash 40 GB of an executable through memory, we can’t help but shake our heads at how even terrible solutions can work. We love seeing someone turn a bad idea into an interesting one, like this desoldering setup.

An Enigma Machine Built In Meccano

June 15, 2024 by 5 Comments

As far as model construction sets go, LEGO is by far the most popular brand for building not only pre-planned models but whatever the builder can imagine. There are a few others out there though, some with some interesting features. Meccano (or Erector in North America) is a construction set based around parts that are largely metal including its fasteners, which allows for a different approach to building models than other systems including the easy addition of electricity. [Craig], a member of the London Meccano Club, is demonstrating his model Enigma machine using this system for all of its parts and adding some electricity to make the circuitry work as well.

The original Enigma machine was an electronic cypher used by the German military in World War 2 to send coded messages. For the time, its code was extremely hard to break, and led to the British development of the first programmable electronic digital computer to help decipher its coded messages. This model uses Meccano parts instead to recreate the function of the original machine, with a set of keys similar to a typewriter which, when pressed, advance a set of three wheels. The wheels all have wiring in them, and depending on their initial settings will light up a different character on a display.

There are a few modifications made to the design (besides the use of a completely different set of materials) but one of the main ones was eliminating the heavy leaf springs of the original for smaller and easier-to-manage coil springs, which are also part of the electrical system that creates the code. The final product recreates the original exceptionally faithfully, with plans to create a plugboard up next, and you can take a look at the inner workings of a complete original here.

Continue reading “An Enigma Machine Built In Meccano” →

Well Documented Code Helps Revive Decades-Old Commodore Project

June 7, 2023 by 15 Comments

In the 1980s, [Mike] was working on his own RPG for the Commodore 64, inspired by dungeon crawlers of the era like Ultima IV and Telengard, both some of his favorites. The mechanics and gameplay were fairly revolutionary for the time, and [Mike] wanted to develop some of these ideas, especially the idea of line-of-sight, even further with his own game. But an illness, a stint in the military, and the rest of life since the 80s got in the way of finishing this project. This always nagged at him, so he finally dug out his decades-old project, dusted out his old Commodore and other antique equipment, and is hoping to finish it by 2024.

Luckily [Mike’s] younger self went to some extremes documenting the project, starting with a map he created which was inspired by Dungeons and Dragons. There are printed notes from a Commodore 64 printer, including all of the assembly instructions, augmented with his handwritten notes to explain how everything worked. He also has handwritten notes, including character set plans, disk sector use plans, menus, player commands, character stats, and equipment, all saved on paper. The early code was written using a machine language monitor since [Mike] didn’t know about the existence of assemblers at the time. Eventually, he discovered them and attempted to rebuild the code on a Commodore 128 and then an Amiga, but never got everything working together. There is some working code still on a floppy disk, but a lot of it doesn’t work together either.

While not quite finished yet, [Mike] has a well-thought-out plan for completing the build, involving aggregating all of the commented source code and doing quarterly sprints from here on out to attempt to get the project finished. We’re all excited to see how this project fares in the future. Beyond the huge scope of this pet project, we’d also suggest that this is an excellent example of thoroughly commenting one’s code to avoid having to solve mysteries or reinvent wheels when revisiting projects months (or decades) later. After all, self-documenting code doesn’t exist.

Continue reading “Well Documented Code Helps Revive Decades-Old Commodore Project” →

Modernizing C Arrays For Greater Memory Safety

February 10, 2023 by 75 Comments

Lately, there has been a push for people to stop using programming languages that don’t promote memory safety. But as we still haven’t seen the death of some languages that were born in the early 1960s, we don’t think there will be much success in replacing the tremendous amount of software that uses said “unsafe” languages.

That doesn’t mean it’s a hopeless cause, though. [Kees Cook] recently posted how modern C99 compilers offer features to help create safer arrays, and he outlines how you can take advantage of these features. Turns out, it is generally easy to do, and if you get errors, they probably point out unexpected behavior in your original code, so that’s a plus.

We don’t think there’s anything wrong with C and C++ if you use them as you should. Electrical outlets are useful until you stick a fork in one. So don’t stick a fork in one. We really liked the recent headline we saw from [Sarah Butcher]: “If you can’t write safe C++ code, it’s because you can’t write C++.” [Cook’s] post makes a similar argument.  C has advanced quite a bit and the fact that 30-year-old code doesn’t use these new features isn’t a good excuse to give up on C.

Continue reading “Modernizing C Arrays For Greater Memory Safety” →

Pocket Radio Powered By Tiny Microcontroller

July 6, 2022 by 33 Comments

Before the days of MP3 players and smartphones, and even before portable CD players, those of us of a certain age remember that our cassette players were about the only way to take music on-the-go. If we were lucky, they also had a built-in radio for when the single tape exhausted both of its sides. Compared to then, it’s much easier to build a portable radio even though cassettes are largely forgotten, as [wagiminator] shows us with this radio design based on an ATtiny.

The build is about as compact as possible, with the aforementioned ATtiny 402/412 as its core, it also makes use of an integrated circuit FM tuner,  an integrated audio amplifier with its own single speaker, and a small OLED display. The unit also boasts its own lithium-polymer battery charger and its user interface consists of only three buttons, plenty for browsing radio stations and controlling volume.

The entire build fits easily in the palm of a hand and is quite capable for a mobile radio, plus all of the schematics and code is available on the project page. While it doesn’t include AM capability, just the fact that FM is this accessible nowadays when a few decades ago it was cutting-edge technology is quite remarkable. If you’re looking for an even smaller FM receiver without some of the bells and whistles of this one, take a look at this project too.

A Programming Language To Express Programming Frustration

December 14, 2021 by 26 Comments

Programming can be a frustrating endeavor. Certainly we’ve all had moments, such as forgetting punctuation in C or messing up whitespace in Python. Even worse, an altogether familiar experience is making a single change to a program that should have resulted in a small improvement but instead breaks the program. Now, though, there’s a programming language that can put these frustrations directly into the code itself into a cathartic, frustration-relieving syntax. The language is called AHHH and it’s quite a scream.

While it may not look like it on the surface, the language is Turing complete and can be used just like any other programming language. The only difference is that there are only 16 commands in this language which are all variants of strings of four capital- or lower-case-H characters. The character “A” in the command “AHHH” starts the program, and from there virtually anything can be coded as a long, seemingly unending scream. The programming language is loosely related to COW which uses various “moos” to create programs instead of screams, and of course is also distantly related to brainfuck which was an esoteric programming language created in order to have the smallest possible compiler.

We can’t really recommend that beginner programmers start to learn this language instead of something more practical like Python, esoteric languages like these can teach us a lot about the way that computers work. This language, for example, lets you code in pixels instead of characters. Others are more for fun such as this language which turns your code into an ’80s rock ballad.

Thanks to [Kyle F] for the tip!