// Write a file so a crash or power cut never leaves half of it: write to a temp file, then rename over the original.
const fs = require('fs');
const crypto = require('crypto');
module.exports = function writeFileAtomic(file, data, opts = { mode: 0o600 }) {
  const tmp = file + '.' + crypto.randomBytes(4).toString('hex') + '.tmp';
  try { fs.writeFileSync(tmp, data, opts); fs.renameSync(tmp, file); }
  catch (e) { try { fs.unlinkSync(tmp); } catch {} throw e; }
};