Deno port of https://gist.github.com/artisonian/d3797f50c3f4fdfc88b1

erudite.ts

import { parse } from "https://deno.land/std@v0.30.0/flags/mod.ts";
import { EOL } from "https://deno.land/std@v0.30.0/path/mod.ts";
import marked from "https://raw.githubusercontent.com/denolib/marked/master/main.ts";

const args = parse(Deno.args);

if (args.h || args.help) {
  printUsage();
  Deno.exit(0);
}

if (!args._.length) {
  printUsage();
  Deno.exit(1);
}

const decoder = new TextDecoder();
const md = decoder.decode(await Deno.readFile(args._[0]));
const tokens = marked.lexer(md);

const codeBlocks = [];
for (const token of tokens) {
  if (token.type !== "code" || !token.lang) continue;
  codeBlocks.push(token.text);
}

const src = codeBlocks.join(EOL + EOL);

const dest = args.o || args.outfile
if (dest) {
  const encoder = new TextEncoder()
  await Deno.writeFile(dest, encoder.encode(src))
} else {
  console.log(src);
}

function printUsage() {
  console.error(`Usage: erudite [options] path/to/filename

  -h, --help     show this help text
  -o, --outfile  write to the given file path (default: stdout)`);
}