A very simplistic command shell for use in environments that give a Node REPL

poor-mans-shell.js

global._poorMansShell = () => {
  const { spawn } = require("child_process");
  const fs = require("fs");
  const path = require("path");
  const readline = require("readline");

  let CURRENT_DIR = process.cwd();

  const READLINE = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
  });

  const getCdIfPresent = (cmd) => {
    const match = /^\s*cd\s+(.*)$/.exec(cmd);
    if (match) return match[1];
  };

  const showPromptForCommand = () =>
    READLINE.question(`${CURRENT_DIR} $ `, (cmd) => {
      const cd = getCdIfPresent(cmd);
      if (cd) {
        if (!cd.startsWith("/")) {
          CURRENT_DIR = path.resolve(path.join(CURRENT_DIR, cd));
        } else {
          CURRENT_DIR = cd;
        }
        return showPromptForCommand();
      }

      fs.writeFileSync(`${__dirname}/tmp.sh`, cmd);
      const proc = spawn("sh", [`${__dirname}/tmp.sh`], {
        cwd: CURRENT_DIR,
        stdio: "inherit",
      });

      proc.on("close", () => showPromptForCommand());
    });
  showPromptForCommand();
};

sh.js

global._sh = function (cmd) {
  const { execSync } = require("child_process");
  const output = execSync(cmd).toString("utf8");
  console.log(output);
  return output;
};