format-key/index.js

#!/usr/bin/env node

const stdin = process.stdin;

if (stdin.isTTY) {
  throw new Error('Standard input required');
  process.exit(1)
}

let key = '';

stdin.setEncoding('utf-8');

stdin.on('readable', () => {
  let chunk;

  while((chunk = stdin.read())) {
    key += chunk;
  }
});

stdin.on('end', () => {
  key = key.replace(/\n/g,'');

  const [header, body, footer] = key
    .replace(/(-----BEGIN\s(RSA\s)?(PUBLIC|PRIVATE)\sKEY-----)/, '$1\n')
    .replace(/(-----END\s(RSA\s)?(PUBLIC|PRIVATE)\sKEY-----)/, '\n$1')
    .split('\n')
    .filter(key => key !== '')

  const result = [header, body.replace(/(.{64})/g, '$1\n'), footer].join('\n');
  console.log(result);
});