Cast Commands

Cast is Foundry's command-line tool for interacting with EVM-compatible blockchains.

When to Use

• Querying contract state (balances, storage, call results)
• Sending transactions
• Calling contract functions
• Converting between data formats
• Debugging transactions
• ENS resolution
• ABI encoding/decoding

Reading Contract State

call - Read-Only Function Calls

# Call a view function
cast call 0xContract "balanceOf(address)(uint256)" 0xAddress

# Call with RPC URL
cast call 0xContract "totalSupply()(uint256)" --rpc-url mainnet

# Call function with multiple return values
cast call 0xContract "getReserves()(uint112,uint112,uint32)"

balance - Get ETH Balance

# Get balance in wei
cast balance 0xAddress --rpc-url mainnet

# Get balance in ether
cast balance 0xAddress --rpc-url mainnet -e

storage - Read Storage Slots

# Read slot 0
cast storage 0xContract 0 --rpc-url mainnet

# Read specific slot
cast storage 0xContract 0x2 --rpc-url mainnet

code - Get Contract Bytecode

# Get deployed bytecode
cast code 0xContract --rpc-url mainnet

Sending Transactions

send - Write Transactions

# Send transaction
cast send 0xContract "transfer(address,uint256)" \
    0xRecipient 1000000000000000000 \
    --rpc-url mainnet \
    --private-key $PRIVATE_KEY

# Send with value (ETH)
cast send 0xContract "deposit()" \
    --value 1ether \
    --rpc-url mainnet \
    --private-key $PRIVATE_KEY

# Send raw ETH transfer
cast send 0xRecipient --value 1ether \
    --rpc-url mainnet \
    --private-key $PRIVATE_KEY

Gas Configuration

# Specify gas limit
cast send 0xContract "mint()" --gas 500000

# Specify gas price (legacy)
cast send 0xContract "mint()" --gas-price 50gwei

# Specify EIP-1559 fees
cast send 0xContract "mint()" \
    --priority-gas-price 2gwei \
    --gas-price 100gwei

ABI Encoding/Decoding

abi-encode - Encode Function Arguments

# Encode function call data
cast abi-encode "transfer(address,uint256)" 0xRecipient 1000

# Encode constructor arguments
cast abi-encode "constructor(string,string,uint8)" "Token" "TKN" 18

abi-decode - Decode Data

# Decode function output
cast abi-decode "balanceOf(address)(uint256)" 0x000...0001

# Decode with multiple outputs
cast abi-decode "getReserves()(uint112,uint112,uint32)" 0x...

calldata - Encode Full Calldata

# Encode function selector + arguments
cast calldata "transfer(address,uint256)" 0xRecipient 1000
# Output: 0xa9059cbb...

# Decode calldata
cast calldata-decode "transfer(address,uint256)" 0xa9059cbb...

sig - Get Function Selector

# Get 4-byte selector
cast sig "transfer(address,uint256)"
# Output: 0xa9059cbb

# Get event signature
cast sig-event "Transfer(address,address,uint256)"

Data Conversion

Numbers

# Hex to decimal
cast to-dec 0xff
# Output: 255

# Decimal to hex
cast to-hex 255
# Output: 0xff

# Convert to wei
cast to-wei 1.5 ether
# Output: 1500000000000000000

# Convert from wei
cast from-wei 1500000000000000000
# Output: 1.5

Units

# Parse units
cast to-unit 1000000000000000000 ether
# Output: 1

# Format units
cast to-wei 100 gwei
# Output: 100000000000

Strings and Bytes

# String to bytes32
cast format-bytes32-string "hello"

# Bytes32 to string
cast parse-bytes32-string 0x68656c6c6f...

# ASCII to hex
cast from-utf8 "hello"

# Hex to ASCII
cast to-ascii 0x68656c6c6f

Addresses

# Checksum address
cast to-checksum-address 0xaddress

# Compute CREATE address
cast compute-address 0xDeployer --nonce 5

# Compute CREATE2 address
cast create2 --starts-with 0000 \
    --deployer 0xDeployer \
    --init-code-hash 0x...

Block & Transaction Info

block - Get Block Data

# Get latest block
cast block latest --rpc-url mainnet

# Get specific block
cast block 18000000 --rpc-url mainnet

# Get block field
cast block latest --field timestamp --rpc-url mainnet

tx - Get Transaction Data

# Get transaction by hash
cast tx 0xTxHash --rpc-url mainnet

# Get specific field
cast tx 0xTxHash --field gasPrice --rpc-url mainnet

receipt - Get Transaction Receipt

# Get receipt
cast receipt 0xTxHash --rpc-url mainnet

# Get logs
cast receipt 0xTxHash --field logs --rpc-url mainnet

logs - Get Event Logs

# Get logs by event signature
cast logs "Transfer(address,address,uint256)" \
    --from-block 18000000 \
    --to-block latest \
    --address 0xTokenContract \
    --rpc-url mainnet

Chain Info

# Get chain ID
cast chain-id --rpc-url mainnet

# Get gas price
cast gas-price --rpc-url mainnet

# Get base fee
cast base-fee --rpc-url mainnet

# Get nonce
cast nonce 0xAddress --rpc-url mainnet

ENS

# Resolve ENS name
cast resolve-name vitalik.eth --rpc-url mainnet

# Lookup address
cast lookup-address 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 --rpc-url mainnet

Wallet Operations

wallet - Manage Keys

# Generate new wallet
cast wallet new

# Get address from private key
cast wallet address --private-key $PRIVATE_KEY

# Sign message
cast wallet sign "message" --private-key $PRIVATE_KEY

# Verify signature
cast wallet verify --address 0xAddress "message" 0xSignature

Debugging

run - Trace Transaction

# Run transaction trace
cast run 0xTxHash --rpc-url mainnet

# Quick trace
cast run 0xTxHash --quick --rpc-url mainnet

4byte - Decode Function Signature

# Lookup function signature
cast 4byte 0xa9059cbb
# Output: transfer(address,uint256)

# Lookup event signature
cast 4byte-event 0xddf252ad...

Utility Commands

keccak - Hash Data

# Keccak256 hash
cast keccak "hello"

# Hash function signature (for selector)
cast keccak "transfer(address,uint256)" | cut -c1-10

concat-hex - Concatenate Hex

cast concat-hex 0x1234 0x5678
# Output: 0x12345678

access-list - Generate Access List

# Generate access list for transaction
cast access-list 0xContract "swap(uint256)" 1000 \
    --rpc-url mainnet

RPC Configuration

Using foundry.toml

[rpc_endpoints]
mainnet = "${MAINNET_RPC_URL}"
sepolia = "${SEPOLIA_RPC_URL}"

# Use named endpoint
cast call 0xContract "totalSupply()(uint256)" --rpc-url mainnet

Environment Variable

export ETH_RPC_URL=https://eth-mainnet.g.alchemy.com/v2/...
cast call 0xContract "totalSupply()(uint256)"

Common Patterns

See patterns.md for more examples.

Check Token Balance

cast call $TOKEN "balanceOf(address)(uint256)" $ADDRESS --rpc-url mainnet | cast to-dec

Approve and Transfer

# Approve
cast send $TOKEN "approve(address,uint256)" $SPENDER $AMOUNT \
    --rpc-url mainnet --private-key $PK

# Transfer
cast send $TOKEN "transferFrom(address,address,uint256)" $FROM $TO $AMOUNT \
    --rpc-url mainnet --private-key $PK

Interact with Uniswap

# Get reserves
cast call $PAIR "getReserves()(uint112,uint112,uint32)" --rpc-url mainnet

# Get price
cast call $ROUTER "getAmountsOut(uint256,address[])(uint256[])" \
    1000000000000000000 "[$WETH,$USDC]" --rpc-url mainnet