cast-commands

# Cast CLI Reference ## Overview `cast` is Foundry's command-line tool for interacting with EVM chains. Read state, send transactions, decode data, and inspect contracts without writing scripts. ## Reading State (cast call) ```bash # Read a view function cast call 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48 \ "balanceOf(address)(uint256)" 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 \ --rpc-url $ETH_RPC_URL # Read with named outputs cast call 0xUniswapV3Pool "slot0()(uint160,int24,uint16,uint16,uint16,uint8,bool)" \ --rpc-url $ETH_RPC_URL # Call at a specific block cast call 0xContract "totalSupply()(uint256)" --block 18000000 --rpc-url $ETH_RPC_URL # Call to another address (simulated msg.sender) cast call --from 0xWhale 0xContract "balanceOf(address)(uint256)" 0xWhale ``` ## Writing State (cast send) ```bash # Send a transaction cast send 0xToken "transfer(address,uint256)" 0xRecipient 1000000 \ --private-key $PRIVATE_KEY --rpc-url $ETH_RPC_URL # Approve spending cast send 0xToken "approve(address,uint256)" 0xSpender $(cast max-uint) \ --private-key $PRIVATE_KEY --rpc-url $ETH_RPC_URL # Send with value (ETH) cast send 0xContract "deposit()" --value 1ether \ --private-key $PRIVATE_KEY --rpc-url $ETH_RPC_URL # Send with gas settings cast send 0xContract "doStuff()" \ --gas-limit 500000 --gas-price 30gwei \ --private-key $PRIVATE_KEY --rpc-url $ETH_RPC_URL ``` ## Storage Inspection (cast storage) ```bash # Read raw storage slot cast storage 0xContract 0 --rpc-url $ETH_RPC_URL # Read specific slot (e.g., ERC-1967 implementation slot) cast storage 0xProxy \ 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc \ --rpc-url $ETH_RPC_URL # Read mapping value: slot = keccak256(key . mappingSlot) # For mapping at slot 2, key = 0xAddress: cast index address 0xAddress 2 # Then read that computed slot cast storage 0xContract $(cast index address 0xAddress 2) ``` ## ABI Encoding / Decoding ```bash # Encode function calldata cast calldata "transfer(address,uint256)" 0xRecipient 1000000 # Decode calldata cast 4byte-decode 0xa9059cbb000000000000000000000000... # Encode constructor arguments cast abi-encode "constructor(string,string,uint256)" "MyToken" "MTK" 1000000 # Decode ABI-encoded data cast abi-decode "balanceOf(address)(uint256)" 0x00000000000000000000000000000000000000000000000000000000000f4240 # Get function selector (first 4 bytes of keccak256) cast sig "transfer(address,uint256)" # Output: 0xa9059cbb # Reverse lookup selector cast 4byte 0xa9059cbb ``` ## Block and Chain Info ```bash # Current block number cast block-number --rpc-url $ETH_RPC_URL # Block details cast block latest --rpc-url $ETH_RPC_URL cast block 18000000 --rpc-url $ETH_RPC_URL # Base fee cast base-fee --rpc-url $ETH_RPC_URL # Gas price cast gas-price --rpc-url $ETH_RPC_URL # Chain ID cast chain-id --rpc-url $ETH_RPC_URL # Client version cast client --rpc-url $ETH_RPC_URL ``` ## Contract Inspection ```bash # Get contract bytecode cast code 0xContract --rpc-url $ETH_RPC_URL # Get contract bytecode size cast code 0xContract --rpc-url $ETH_RPC_URL | wc -c # Generate interface from Etherscan cast interface 0xContract --etherscan-api-key $ETHERSCAN_API_KEY # Download verified source from Etherscan cast etherscan-source 0xContract --etherscan-api-key $ETHERSCAN_API_KEY -d ./source ``` ## Account and Balance ```bash # ETH balance cast balance 0xAddress --rpc-url $ETH_RPC_URL cast balance 0xAddress --rpc-url $ETH_RPC_URL --ether # human-readable # Nonce cast nonce 0xAddress --rpc-url $ETH_RPC_URL # Resolve ENS cast resolve-name vitalik.eth --rpc-url $ETH_RPC_URL cast lookup-address 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 --rpc-url $ETH_RPC_URL ``` ## Transaction Inspection ```bash # Get transaction details cast tx 0xTxHash --rpc-url $ETH_RPC_URL # Get transaction receipt cast receipt 0xTxHash --rpc-url $ETH_RPC_URL # Decode transaction input cast 4byte-decode $(cast tx 0xTxHash input --rpc-url $ETH_RPC_URL) # Trace a transaction (requires archive node) cast run 0xTxHash --rpc-url $ETH_RPC_URL ``` ## Conversion Utilities ```bash # Wei to ether cast from-wei 1000000000000000000 # Output: 1.000000000000000000 # Ether to wei cast to-wei 1.5 # Output: 1500000000000000000 # Hex to decimal cast to-dec 0xff # Output: 255 # Decimal to hex cast to-hex 255 # Output: 0xff # Keccak256 hash cast keccak "Transfer(address,address,uint256)" # Max uint256 cast max-uint # Output: 115792089237316195423570985008687907853269984665640564039457584007913129639935 ``` ## Common One-Liners ```bash # Check if address is a contract cast code 0xAddress --rpc-url $ETH_RPC_URL | grep -q "^0x$" && echo "EOA" || echo "Contract" # Get USDC balance (6 decimals) cast call 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48 \ "balanceOf(address)(uint256)" 0xAddress --rpc-url $ETH_RPC_URL | \ xargs -I{} cast from-wei {} 6 # Read ERC-1967 proxy implementation cast storage 0xProxy \ 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc \ --rpc-url $ETH_RPC_URL # Simulate a swap (static call) cast call 0xRouter \ "getAmountsOut(uint256,address[])(uint256[])" \ 1000000000000000000 "[0xWETH,0xUSDC]" \ --rpc-url $ETH_RPC_URL # Estimate gas for a transaction cast estimate 0xContract "doStuff(uint256)" 42 --rpc-url $ETH_RPC_URL # Watch for new blocks cast block-number --rpc-url $ETH_RPC_URL --watch ``` ## Tips - Set `ETH_RPC_URL` environment variable to avoid `--rpc-url` on every command - Use `--json` flag for machine-readable output - Pipe cast output to other cast commands for complex queries - Use `cast wallet` subcommands for key management - `cast completions bash/zsh/fish` generates shell completions