buidler.config.js

usePlugin("@nomiclabs/buidler-web3");

task("balance", "Prints an account's balance")
 .addParam("account", "The account's address")
 .setAction(async taskArgs => {
     const account = web3.utils.toChecksumAddress(taskArgs.account);
     const balance = await web3.eth.getBalance(account);

     console.log(web3.utils.fromWei(balance, "ether"), "ETH");
 });

module.exports = {};