begrudge: convert ANSI-escaped colorized terminal output to classed HTML

begrudge(1) is a small tool written in Zig to convert colorized terminal output that uses ANSI escape sequences into class-based HTML snippets. It may be useful for converting the output of tools such as bat(1) or glow(1) into something web browsers can understand, without the need to reinvent or even modify those renderers.

begrudge does not attempt to implement all known ANSI escape sequence commands or the entire Paul Flo Williams state machine, instead implementing the same subset as a2h(1), a similar tool written in Ruby (though a2h's code was not used here), thus, the following escape sequences are supported:

<ESC>[0m
    Resets all attributes / closes all HTML tags.
<ESC>[1m=<span class='begrudge-bold'>
    Bold.
<ESC>[4m=<span class='begrudge-underscore'>
    Underscore.
<ESC>[5m=<span class='begrudge-blink'>
    Blink. For goodness' sake, please don't actually make your CSS blink this.
<ESC>[8m=<span class='begrudge-span'>
    Hidden.
<ESC>[30-37m=<span class='begrudge-fg-0'>
    Foreground color (30 -> 0, 37 -> 7, you get the idea).
    Escape 38, "default color", is not yet implemented.
<ESC>[40-47m=<span style='background-color:color>
    Background color (40 -> 0, 47 -> 7, you get the idea).
    Escape 48, "default color", is not yet implemented.
<ESC>[90-97m=<span style='color:color>
    Bright foreground color (90 -> 0, 97 -> 7, you get the idea).
<ESC>[100-107m=<span style='background-color:color>
    Bright background color (100 -> 0, 107 -> 7, you get the idea).

I personally consider truecolor (full rgb) terrible UX (if I set a 16 colour palette, use it, damn it, I don't care about your design choices) and thus will stubbornly be refusing to implement support for it for now. if you hate this decision, you have three options:

• write it in a fork and go on to achieve world domination with said fork, to which I could well remain blissfully ignorant forever
• write it and submit a patch. I'll merge it if it's clean, tested code, even if it will, I insist, bring disorder and chaos to the cosmos
• bug me about it until I cave and write a truecolor to <span style=...> translator some time in the next few decades, maybe

Getting Started

To my knowledge, begrudge is not yet packaged anywhere. You'll need to build it from source using a Zig 0.11 compiler. The standard zig build workflow is supported (and will be used in the below examples, though you're free to copy the resultant binary to wherever). There are no dependencies outside of the standard library. On Linux, at least, the produced binary has no sofile (dynamic linking) dependencies at runtime, either.

begrudge has no command line arguments: simply pipe ANSI-escaped data into it, and it will spit out the HTML span-ified version to standard output. For example, to render begrudge's own source via bat, which uses syntect's engine under the hood:

bat -fp --theme=ansi begrudge.zig | zig build -Drelease-fast run

# ...
# <span class='begrudge-fg-5'>const</span> std <span class='begrudge-fg-5'>=</span> <span class='begrudge-fg-5'>@import</span>(<span class='begrudge-fg-2'>"std"</span>);
# <span class='begrudge-fg-5'>const</span> eql <span class='begrudge-fg-5'>=</span> std.mem.eql;
# <span class='begrudge-fg-5'>const</span> expect <span class='begrudge-fg-5'>=</span> std.testing.expect;
# <span class='begrudge-fg-5'>const</span> expectEqual <span class='begrudge-fg-5'>=</span> std.testing.expectEqual;
# <span class='begrudge-fg-5'>const</span> expectEqualStrings <span class='begrudge-fg-5'>=</span> std.testing.expectEqualStrings;
# <span class='begrudge-fg-5'>const</span> trimLeft <span class='begrudge-fg-5'>=</span> std.mem.trimLeft;

To integrate with glow, try PAGER="zig build -Drelease-fast run" glow -p README.md (however, note that glow's output is not especially polite - it has a tendency to set styles, print a single character, reset the terminal, and repeat, over and over and over. This leads to very large, albeit compressable, output HTML).

You could extend this further, perhaps wrapping the entire thing in <pre>, writing a stylesheet mapping the couple dozen possible classes to CSS styles, and putting it on your blog as a snippet system. You may also be interested in my other project (that spawned the idea for begrudge in the first place), gawsh (still under extremely early development at time of writing).

Development Notes

All commits should pass make lint and make test (CI will probably exist eventually). begrudge uses Chronologic Versioning 2019.05.19, tagged whenever the main branch looks good for a release. It's super informal, because this is a tiny tool that is unlikely to change often, if at all.