Scripting

Forge scripts are Solidity files that deploy contracts and execute transactions on-chain. They replace deployment scripts traditionally written in JavaScript.

Script structure

Scripts inherit from Script and implement a run() function:

script/Deploy.s.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;
 
import {Script} from "forge-std/Script.sol";
import {Counter} from "../src/Counter.sol";
 
contract DeployScript is Script {
    function run() public {
        vm.startBroadcast();
        
        Counter counter = new Counter();
        counter.setNumber(42);
        
        vm.stopBroadcast();
    }
}

Key elements:

Inherit from forge-std/Script.sol
Script files end with .s.sol
Wrap deployment logic in vm.startBroadcast() / vm.stopBroadcast()

Running scripts

Simulate a deployment (no transactions sent):

$ forge script script/Deploy.s.sol

Broadcast transactions to a network:

$ forge script script/Deploy.s.sol --broadcast --rpc-url $RPC_URL

Providing a private key

$ forge script script/Deploy.s.sol --broadcast --rpc-url $RPC_URL --account deployer

Broadcasting from a specific address

To broadcast from a specific address:

vm.startBroadcast(deployerAddress);

Or use the key at a specific index from a mnemonic:

uint256 deployerPrivateKey = vm.envUint("PRIVATE_KEY");
vm.startBroadcast(deployerPrivateKey);

Verifying deployed contracts

Verify on Etherscan during deployment:

$ forge script script/Deploy.s.sol \
    --broadcast \
    --rpc-url $RPC_URL \
    --verify \
    --etherscan-api-key $ETHERSCAN_API_KEY

Resuming failed broadcasts

If a broadcast fails partway through, resume from where it left off:

$ forge script script/Deploy.s.sol --broadcast --rpc-url $RPC_URL --resume

Multi-chain deployments

Deploy to multiple chains by running the script with different RPC URLs:

$ forge script script/Deploy.s.sol --broadcast --rpc-url $MAINNET_RPC
$ forge script script/Deploy.s.sol --broadcast --rpc-url $ARBITRUM_RPC
$ forge script script/Deploy.s.sol --broadcast --rpc-url $OPTIMISM_RPC

Reading deployment artifacts

Scripts write transaction receipts to broadcast/. Access deployed addresses in subsequent scripts:

function run() public {
    string memory json = vm.readFile("broadcast/Deploy.s.sol/1/run-latest.json");
    address counter = vm.parseJsonAddress(json, ".transactions[0].contractAddress");
}

Script cheatcodes

Scripts have access to all cheatcodes. Common ones for scripting:

// Read environment variables
string memory rpcUrl = vm.envString("RPC_URL");
uint256 privateKey = vm.envUint("PRIVATE_KEY");
 
// Read/write files
string memory config = vm.readFile("config.json");
vm.writeFile("output.txt", "deployed");
 
// Parse JSON
address addr = vm.parseJsonAddress(json, ".address");
 
// Console logging
console.log("Deploying to:", block.chainid);

Dry run

Test a script without sending transactions:

$ forge script script/Deploy.s.sol --rpc-url $RPC_URL

This simulates against the live chain state and shows what would happen.

Was this helpful?

Suggest changes on GitHub