🖥️ My ultra-budget server powering http://websysctl.alfonsosiciliano.net has been running smoothly for the past 2 months. So far, so good!

📈 #Crawlers hit tens of thousands of sysctl parameter pages daily. That's fine, since robots.txt allows it. But why keep requesting non-existent pages as if the site were built with WordPress 😤 ? Fortunately, the stack (#FreeBSD + #OpenResty 🌐 + #Lapis ✏️ + a custom-built #database 📦 ) stays well within the limited resources of my $5/month cloud server.

The code might soon be #OpenSource stay tuned!

#UNIX #sysctl #WebDev #WebServer #ThePowerToServe #coding #Lua #kernel

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Screenshot of the "Tree MIB" page from the WebSysctl site. The left panel shows an expandable tree view of the FreeBSD sysctl MIB hierarchy, with nodes like sysctl, kern, vm, sys, security, and their subcategories. The security.mac.mmap_revocation_via_cow node is selected. The right panel displays detailed information about this sysctl parameter, including its link, OID, name, description ("Revoke mmap access to files via copy-on-write semantics, or by removing all write access"), type (integer), format (I), flags (RD, WR, MPSAFE), label, and handler status (Defined). The top navigation bar includes links: Home, Docs, Table, Tree (highlighted), Update, Login, and Contacts.

Weekend goal: a #Lua chunk (script) to help sighted users review #Braille. It's a great way to understand how visually impaired users interact with a computer using a screen reader and a Braille display. The script is simple and easy to configure. Currently, it offers a learning mode; in the future, a challenge mode will be added, along with a blog post explaining how to set it up.

Link: https://gitlab.com/-/snippets/4858299

On #FreeBSD it should be executable via flua:
% flua learnbraille.lua

after installing liblouis:
# pkg install liblouis

#UNIX #script #scripting #accessibility #inclusion

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Terminal screenshot of a Lua script called learnbraille.lua running on FreeBSD. The script is titled "LearnBraille 0.0.1" and uses a Braille conversion table. It quizzes the user with Braille character patterns and expects input of the corresponding character. The session shows a sequence of questions with user responses and feedback indicating whether the answer was correct or not. The script is launched using the command lua54 learnbraille.lua.

Some notable users of #Lua (beside @silverbulletmd of course):

Pico 8 https://www.lexaloffle.com/dl/docs/pico-8_manual.html
LOVE https://www.love2d.org/
Dwarf fortress: https://dwarffortresswiki.org/index.php/Lua_scripting
Neovim: https://neovim.io/doc/user/lua.html
Pandoc: https://pandoc.org/lua-filters.html
Roblox: https://luau.org/
Openresty https://openresty.org/en/
Minetest https://www.minetest.net/
Redis: https://redis.io/docs/latest/develop/interact/programmability/eval-intro/
ScyllaDB: https://opensource.docs.scylladb.com/stable/cql/functions.html

Some thoughts on what makes #Lua special in my mind:

1. The language is small and easy to learn. If you know any other procedural language, you will pick it up in a few hours tops.

2. Since Lua is designed to be embedded in an existing application, it doesn’t come with a huge general purpose library you have to learn. Like (1) lowering the barrier to entry.

3. This context suits a dynamic language very well. Little ceremony. Code that is straight to the point.

4. Cultural observation: since Lua is often used in more “casual” programming settings (game development, editor customization, environment tweaking) with relatively low stakes, practices that “proper” software engineering practice would oppose, become acceptable for convenience and productivity. Global variables? YOLO. Unit tests? Nah. Just get shit done.

Ok. Day one of using @silverbulletmd in #Vim mode lead to already fixing some ugly UI glitches. Now thinking how to expand #Lua APIs to define Vim commands, bindings and other things. Also a reason to dive a bit deeper into @neovim which leans heavily on Lua. Also an interesting source of inspiration for Lua API design potentially.

Ok, so I’m now a few months into building a custom (almost from scratch) #Lua implementation for @silverbulletmd dubbed #SpaceLua (for reasons).

A few things that panned out really well, and a few surprises that I did not anticipate:

0. General recommendation: don’t do this. Don’t just implement a full programming language because you think it’s a good idea. I also told this myself. It didn’t work. It was a “I’ve don’t this stuff before, I can do it again” type of deal. I was mostly right. But don’t do this.

1. Initially I opted for a custom interpreter (implemented in TypeScript) because I wanted to expose asynchronous (promise based) JS APIs to Lua, and I didn’t see how to do that nicely with a #Wasm-compiled version of the official Lua interpreter. Also I felt that having full control of the running system would turn out to be valuable down the line (I was right on this one).

2. I got the parser part mostly free. I found an existing Lua grammar for the Lezer parser library that #SilverBullet uses. Had to add a few things and had some struggles. This part was pretty seamless with a few glitches here and there.

3. Implementing the core interpreter runtime was actually quite easy. Lua is a mostly simple and small language. Again, I’ve done this before so that helped. Writing good test suites makes this doable and AI helped a lot generating those test suites (because it knows Lua).

4. What I didn’t anticipate is the pain in implementing the full Lua API, especially the `string.*` one which has its own pattern matching language (similar but distinct from regular expressions), which honestly I could do without. But it’s there, and people want to use it, so I need a full implementation. Issues keep coming up, though.

This is what #FOSS promises to be, and it does feel nice to actually do it.