Skills

347 Articles

Linux Fu: Automatic Header File Generation

November 8, 2021 by 22 Comments

I’ve tried a lot of the “newer” languages and, somehow, I’m always happiest when I go back to C++ or even C. However, there is one thing that gets a little on my nerves when I go back: the need to have header files with a declaration and then a separate file with almost the same information duplicated. I constantly make a change and forget to update the header, and many other languages take care of that for you. So I went looking for a way to automate things. Sure, some IDEs will automatically insert declarations but I’ve never been very happy with those for a variety of reasons. I wanted something lightweight that I could use in lots of different toolsets.

I found an older tool, however, that does a pretty good job, although there are a few limitations. The tool seems to be a little obscure, so I thought I’d show you what makeheaders — part of the Fossil software configuration management system. The program dates back to 1993 when [Dwayne Richard Hipp] — the same guy that wrote SQLite — created it for his own use. It isn’t very complex — the whole thing lives in one fairly large C source file but it can scan a directory and create header files for everything. In some cases, you won’t need to make big changes to your source code, but if you are willing, there are several things you can do.

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Basics Of Remote Cellular Access: Watchdogs

October 14, 2021 by 21 Comments

When talking about remote machines, sometimes we mean really remote, beyond the realms of wired networks that can deliver the Internet. In these cases, remote cellular access is often the way to go. Thus far, we’ve explored the hardware and software sides required to control a machine remotely over a cellular connection.

However, things can and do go wrong. When that remote machine goes offline, getting someone on location to reboot it can be prohibitively difficult and expensive. For these situations, what you want is some way to kick things back into gear, ideally automatically. What you’re looking for is a watchdog timer!

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Need A New Programming Language? Try Zig

October 5, 2021 by 131 Comments

Maybe you’ve heard of it, maybe you haven’t. Zig is a new programming language that seems to be growing in popularity. Let’s do a quick dive into what it is, why it’s unique, and what sort of things you would use it for. (Ed Note: Other than “for great justice“, naturally.)

What Is It?

You’ve likely heard of Rust as it has made significant inroads in critical low-level infrastructures such as operating systems and embedded microcontrollers. As a gross oversimplification, it offers memory safety and many traditional runtime checks pushed to compile time. It has been the darling of many posts here at Hackaday as it offers some unique advantages. With Rust on the rise, it makes sense that there might be some space for some new players. Languages like Julia, Go, Swift, and even Racket are all relative newcomers vying for the highly coveted mindshare of software engineers everywhere.

So let’s talk Zig. In a broad sense, Zig is really trying to provide some of the safety of Rust with the simplicity and ease of C. It touts a few core features such as:

  • No hidden control flow
  • No hidden memory allocations
  • No preprocessor, no macros
  • First-class support for optional standard library
  • Interoperable by design
  • Adjustable Runtime Safety
  • Compile-time code-execution

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Troubleshooting: A Method For Solving Problems The Right Way

September 3, 2021 by 48 Comments

We’ve all experienced that magic moment when, after countless frustrating hours of experimentation and racking your brain, the object of our attention starts working. The 3D printer finally produces good output. The hacked up laptop finally boots. The car engine finally purrs. The question is, do we know why it started working?

This is more important than you might think. Knowing the answer lets you confirm that the core problem was solved, otherwise you may have just fixed a symptom. And lack of understanding means fixing one problem may just create another.

The solution is to adopt a methodical troubleshooting method. We’re talking about a structured problem solving technique that when used properly can help us solve a problem at its core without leaving any loose ends. Such methodology will also leave you knowing why any solution did or didn’t work in the end, and will give you reproducible results.

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Hands-On Review: TCam-Mini WiFi Thermal Imager

July 27, 2021 by 30 Comments

A thermal camera is a tool I have been wanting to add to my workbench for quite a while, so when I learned about the tCam-Mini, a wireless thermal camera by Dan Julio, I placed an order. A thermal imager is a camera whose images represent temperatures, making it easy to see things like hot and cold spots, or read the temperature of any point within the camera’s view. The main (and most expensive) component of the tCam-Mini is the Lepton 3.5 sensor, which sits in a socket in the middle of the board. The sensor is sold separately, but the campaign made it available as an add-on.

Want to see how evenly a 3D printer’s heat bed is warming up, or check whether a hot plate is actually reflowing PCBs at the optimal temperature? How about just seeing how weird your pets would look if you had heat vision instead of normal eyes? A thermal imager like the tCam-mini is the tool for that, but it’s important to understand exactly how the tCam-mini works. While it may look like a webcam, it does not work like one.

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Social Engineering And Menus

July 1, 2021 by 59 Comments

If you follow cybersecurity hacker methods — or just watch Mr. Robot — you probably know that the best way to get someone’s password is to ask for it. Sure, you probably can’t just say “Hi, I’m a bad guy. Can I have your password?” But there are all sorts of tricks you can use like pretending to be in the person’s IT department, someone in management, or by making up a crisis to overcome their better judgement with a sense. But of course, as wise computer people, we are immune to such things, right? We also don’t need those kinds of tricks in our arsenal.

Is that true? It is amazing how many subtle things influence what we think are rational decisions, no matter who we are. Consider going to eat in a restaurant. Simple, right? You look at the menu, pick what you want, and order. No one is influencing you. But they are. According to a BBC article, there’s a whole industry of menu “engineering” that figures out how to get you to order pricey food.

You might not think social engineering for menus is a great skill for us. But maybe your new open source project needs collaborators. Maybe your startup company needs investors. Maybe you’d like someone to look at your resume. Maybe the same tricks that work with diners will work in those cases, too.

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Linux Fu: Shell Script File Embedding

April 9, 2021 by 25 Comments

You need to package up a bunch of files, send them somewhere, and do something with them at the destination. It isn’t an uncommon scenario. The obvious answer is to create an archive — a zip or tar file, maybe — and include a shell script that you have to tell the user to run after unpacking.

That may be obvious, but it assumes a lot on the part of the remote user. They need to know how to unpack the file and they also need to know to run your magic script of commands after the unpack. However, you can easily create a shell script that contains a file — even an archive of many files — and then retrieve the file and act on it at run time. This is much simpler from the remote user’s point of view. You get one file, you execute it, and you are done.

In theory, this isn’t that hard to do, but there are a lot of details. Shell scripts are not compiled — at least, not typically — so the shell only reads what it needs to do the work. That means if your script is careful to exit, you can add as much “garbage” to the end of it as you like. The shell will never look at it, so it’s possible to store the payload there.

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