Bash script

6 Articles

Preview Markdown In The Terminal With Bash

June 17, 2024 by 12 Comments

Markdown has become an extremely popular way to document source code and other projects, thanks in no small part to how well web-based services like GitHub render it. Just sprinkle a few extra characters into a regular text file, and all of a sudden it looks like you know what you’re doing. Unfortunately, there are some places where markdown won’t actually render, and you’ll be stuck looking at those extra characters.

But thanks to MarCLIdown, the terminal doesn’t have to be one of those places. Written by [NihaAlGhul], this simple tool takes a given markdown file and spits out a fairly impressive rendering — and you don’t even need to have one of those fancy new GPU-accelerated terminals. Most impressively, the whole thing is implemented as a single Bash script.

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Amber Compiles To Bash

May 22, 2024 by 17 Comments

It certainly isn’t a new idea to compile a language into an intermediate language. The original C++ compiler outputs C code, for example. Enhanced versions of Fortran were often just conversions of new syntax to old syntax. Of course, it makes sense to output to some language that can run on lots of different platforms. So, using that logic, Amber makes perfect sense. It targets — no kidding — bash. You write with nice modern syntax and compile-time checks. The output is a bash script. Admittedly, sometimes a hard-to-read bash script, but still.

If you want to see the source code, it is available on GitHub. Since Windows doesn’t really support bash — if you don’t count things like Cygwin and WSL — Amber only officially supports Linux and MacOS. In addition to compiling files, Amber can also execute scripts directly which can be useful for a quick one-liner. If you use Visual Studio Code, you can find a syntax highlighter extension for Amber.

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Suc Aims To Replace Slack In Five Lines Of Bash

July 10, 2023 by 43 Comments

The design philosophy of Unix is fairly straightforward. Software should do one thing as simply as possible, and do that one thing only. As a design principle this is sound advice even well outside of the realm of Unix, and indeed software in general, but that doesn’t stop modern software packages from being too large for their own good. So, if you’re tired of bloated chat programs like Slack or Mattermost with their millions of lines of code, you might instead favor something like Simple Unix Chat (suc).

The idea is that suc can perform almost all modern chat functions in only five lines of Bash, supporting rich-text chat, file sharing, access control, and encryption. These five lines, though, only perform the core function of suc — which is to write text to a file on the system. Indeed, suc makes liberal use of plenty of other Unix services which do not add to the line counts, such as the use of SSH to handle authentication. It also relies on some other common Unix system features to handle things like ownership and access for the text files that host the text for the chat.

As channels are simply text files, it makes writing bots or other tools exceptionally simple. You can also easily pipe the output of commands directly into suc with one-liners that can do things like dump the output of make into a specific channel if compilation fails.

While it’s not likely that everyone will ditch tools like Slack to switch to something like this, it’s still an impressive demonstration of what can be done when designing around the Unix philosophy and taking advantage of system tools that already exist rather than reinventing the wheel and re-programming all of those tools into the application. Practices like this might decrease development time and increase the ease of developing cross-platform applications but they often also produce a less than desirable user experience.

Repairing 200+ Raspberry Pis For A Good Cause

January 25, 2021 by 37 Comments

If somebody told you they recently purchased over 200 Raspberry Pis, you might think they were working on some kind of large-scale clustering project. But in this case, [James Dawson] purchased the collection of broken single-board computers with the intention of repairing them so they could be sent to developing countries for use in schools. It sounds like the logistics of that are proving to be a bit tricky, but we’re happy to report he’s at least made good progress on getting the Pis back up and running.

He secured this trove of what he believes to be customer returned Raspberries or the princely sum of £61 ($83 USD). At that price, even if only a fraction ended up being repairable, you’d still come out ahead. Granted all of these appear to be the original Model B, but that’s still a phenomenal deal in our book. Assuming of course you can find some reasonable way to triage them to sort out what’s worth keeping.

To that end, [James] came up with a Bash script that allowed him to check several hardware components including the USB, Ethernet, I2C, and GPIO. With the script on an SD card and a 3.5″ TFT plugged into the Pi’s header for output, he was able to quickly go through the box to get an idea of what sort of trouble he’d gotten himself into. He was only about half way through the process when he wrote this particular blog post, but by that point, he’d found just 40 Pis which wouldn’t start at all. He suspects these might be victims of some common issue in the power circuitry that he’ll investigate at a later date.

A metal ruler made short work of bent pins.
A nasty, but repairable, problem.

The majority of Pis he checked were suffering from nothing worse than some bent GPIO pins or broken SD card slots. Some of the more abused examples had their USB ports ripped off entirely, but were otherwise fine. Another 10 had dead Ethernet, and 4 appear to have damaged traces leading to their HDMI ports. While we’re interested in hearing if [James] can get those 40 dark Pis to fire back up, so far the results are quite promising.

Donating hardware is always a tricky thing, so for now [James] says he’ll be selling the repaired Pis on eBay and donating the proceeds to the Raspberry Pi Foundation so they can continue to develop hardware that will (potentially) accomplish their goal of giving students all over the world a functional computer.

Linux-Fu: One At A Time, Please! Critical Sections In Bash Scripts

August 18, 2020 by 12 Comments

You normally think of a critical section — that is, a piece of a program that excludes other programs from using a resource — as a pretty advanced technique. You certainly don’t often think of them as part of shell scripting but it turns out they are surprisingly useful for certain scripts. Most often, a critical section is protecting some system resource like a shared memory location, but there are cases where a shell script needs similar protection. Luckily, it is really easy to add critical sections to shell scripts, and I’ll show you how.

Sometimes Scripts Need to Be Selfish

One very common case is where you want a script to run exactly one time. If the same script runs again while the original is active, you want to exit after possibly printing a message. Another common case is when you are updating some file and you need undisturbed access while making the change.

That was actually the case that got me thinking about this. I have a script — may be the subject of a future Linux-Fu — that provides dynamic DNS by altering a configuration file for the DNS server. If two copies of the script run at the same time, it is important that only one of them does modifications. The second copy can run after the first is totally complete.

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Custom Weather Camera Feed With Software Tricks

July 23, 2020 by 4 Comments

With a gorgeous view of the Italian seaside, we’re not surprised [Danilo Larizza] had a couple IP cameras set up to pull in real-time views. But using a Raspberry Pi, an environmental sensor, and some software trickery to overlay the current (and naturally, perfect) weather conditions over the images? Now he’s just teasing us.

Whatever his motives are, we have to admit that the end result is very nice. Especially when you find out that there’s no complex hardware or software at work here. An original Raspberry Pi is doing all the heavy lifting by pulling a frame from the external IP camera using ffmpeg, polling the I2C-connected BME280 temperature and humidity sensor with a Python script, and then producing a final snapshot with the environmental data laid over top using ImageMagick.

[Danilo] gives the exact commands he’s using for each step of the process, making it easy to follow along and see how everything comes together in the end. That also makes it much easier to adapt for your own purposes should you feel so inclined. Once you see how all the pieces fit together, where the data and images come from is up to you.

We’ve previously shown how some simple Python code can be used to turn your raw data into attractive images, and combining that with real-world photographs is an excellent way of turning a text file full of values into a display worth showing off.