Setup & Walkthrough

An introduction to Foundry and using the cast function, replacing complex scripts that may otherwise require multiple rpc calls and other functions in between with a single command.

Foundry is a fast and modular toolkit for Ethereum application development written in Rust. It provides four main command-line tools—forge, cast, anvil, and chisel—to streamline everything from project setup to live-chain interactions.

Among these, cast serves as your "Swiss-army knife" for JSON-RPC calls, letting you execute tedious day-to-day tasks (like sending raw transactions, querying balances, fetching blocks, and looking up chain metadata) with simple, consistent commands instead of verbose curl scripts.

This guide walks you through installing Foundry, configuring your environment, and using the most common cast commands to accelerate your development workflow.

Installation & Setup

Install Foundry

Run the following command to install foundryup, the Foundry toolchain installer. This will give you the four main binaries.

curl -L https://foundry.paradigm.xyz | bash
foundryup

After installation, you can switch to the nightly builds for the latest features, though this is optional.

foundryup -i nightly

Verify Installation

Check that each binary was installed correctly by running:

foundryup --version
cast --version
forge --version
anvil --version

You should see version outputs for each tool (e.g., cast 0.2.0).

Configuration

To avoid passing the --rpc-url flag with every command, you can set defaults in a foundry.toml file. This file can be placed in your project's root directory for project-specific settings, or you can create a global configuration at ~/.foundry/foundry.toml for settings you use across all projects.

Here is an example of a global configuration for connecting to a local Ontomir EVM node:

# ~/.foundry/foundry.toml

# Declare your named endpoints (optional; for forge test / forking)
[rpc_endpoints]
Ontomir = "<evm_rpc_url>"

# Configure the default profile for cast/forge/anvil
[profile.default]
# Tell Foundry which chain you're targeting:
chain_id     = 4321
# Directly tell cast to use your endpoint:
eth_rpc_url  = "<evm_rpc_url>"
# Set EVM version for Solidity compilation
evm_version  = "istanbul"

With this global configuration, Foundry tools will automatically connect to your local node without needing additional flags.

Basic Usage of cast

cast replaces the need for custom shell scripts and verbose curl commands by offering first-class RPC commands.

Chain Metadata

• Get Chain ID

  cast chain-id --rpc-url local

  Returns the chain ID in decimal format.

• Get Client Version

  cast client --rpc-url local

  Displays the client implementation and version (e.g., reth/v1.0.0).

cast Command Reference

Chain Commands

Command	Purpose
cast chain	Show the symbolic name of the current chain.
cast chain-id	Fetch the numeric chain ID.
cast client	Get the JSON-RPC client version.

Example:

# Assuming FOUNDRY_RPC_URL is set or using a configured alias
cast chain
cast chain-id
cast client

Transaction Commands

Command	Purpose
cast send	Sign and publish a transaction.
cast publish	Publish a raw, signed transaction.
cast receipt	Fetch the receipt for a transaction hash.
cast tx	Query transaction details (status, logs, etc.).
cast rpc	Invoke any raw JSON-RPC method.

• Sign and Send (using a private key or local keystore):

  cast send 0xRecipientAddress "transfer(address,uint256)" "0xSomeOtherAddress,100" --private-key $YOUR_PK

• Publish Raw Transaction (hex-encoded):

  cast publish 0xf86b808504a817c80082520894...

• Generic RPC Call:

  cast rpc eth_sendRawTransaction 0xf86b8085...

Account & Block Commands

Command	Purpose
cast balance	Get an account's balance (supports ENS and units).
cast block	Fetch block information by number or hash.
cast block-number	Get the latest block number.
cast logs	Query event logs.

• Get Balance (with unit flag):

  # Using an ENS name on Ethereum mainnet
  cast balance vitalik.eth --ether --rpc-url https://eth.merkle.io

• Get Block Details:

  cast block latest

Utility & Conversion Commands

Command	Purpose
cast estimate	Estimate gas for a call or deployment.
cast find-block	Find a block by its timestamp.
cast compute-address	Calculate a CREATE2 address.
cast from-bin	Decode binary data to hex.
cast from-wei	Convert wei to a more readable unit (e.g., ether).
cast to-wei	Convert a unit (e.g., ether) to wei.
cast abi-encode	Encode function arguments.
cast keccak	Hash data with Keccak-256.

These commands allow you to drop one-off scripts for common conversions and estimations.

Streamlining Repetative / Tedious tasks

When performing testing or development roles you may find yourself doing one or more small but very tedious tasks frequently. In your shell's configuration file (~/.bashrc, ~/.zshrc), you can alias cast with your default RPC URL (or multiple on various chains) to save time.

# Set your default RPC endpoint
export CDEV_RPC="<evm_rpc_url>"
# Create an alias
alias ccast='cast --rpc-url $CDEV_RPC'

# Now you can run commands like:
ccast balance 0x...

This is an extremely basic example of how you can improve your workflows by building upon the heavy lifting Foundry already does out of the box.