# Global Variables

### Block and Transaction Properties

* `blockhash(uint blockNumber) returns (bytes32)`: hash of the given block when `blocknumber` is one of the 256 most recent blocks; otherwise returns zero
* `block.basefee (uint)`: current block’s base fee
* `block.chainid (uint)`: current chain id
* `block.coinbase (address payable)`: current block miner’s address
* `block.gaslimit (uint)`: current block gaslimit
* `block.number (uint)`: current block number
* `block.timestamp (uint)`: current block timestamp as seconds since unix epoch
* `gasleft() returns (uint256)`: remaining gas
* `msg.data (bytes calldata)`: complete calldata
* `msg.sender (address)`: sender of the message (current call)
* `msg.sig (bytes4)`: first four bytes of the calldata (i.e. function identifier)
* `msg.value (uint)`: number of wei sent with the message
* `tx.gasprice (uint)`: gas price of the transaction
* `tx.origin (address)`: sender of the transaction (full call chain)

### Error handling

* `assert(bool condition)`: causes a Panic error and thus state change reversion if the condition is not met - to be used for internal errors.
* `require(bool condition)`: reverts if the condition is not met - to be used for errors in inputs or external components.
* `require(bool condition, string memory message)`: reverts if the condition is not met - to be used for errors in inputs or external components. Also provides an error message.
* `revert()`: abort execution and revert state changes
* `revert(string memory reason)`: abort execution and revert state changes, providing an explanatory string

### Members of Address Types

* `<address>.balance (uint256)`: balance of the Address in Wei
* `<address>.code (bytes memory)`: code at the Address (can be empty)
* `<address>.codehash (bytes32)`: the codehash of the Address
* `<address payable>.transfer(uint256 amount)`: send given amount of Wei to Address, reverts on failure, forwards 2300 gas stipend, not adjustable
* `<address payable>.send(uint256 amount) returns (bool)`: send given amount of Wei to Address, returns false on failure, forwards 2300 gas stipend, not adjustable
* `<address>.call(bytes memory) returns (bool, bytes memory)`: issue low-level CALL with the given payload, returns success condition and return data, forwards all available gas, adjustable
* `<address>.delegatecall(bytes memory) returns (bool, bytes memory)`: issue low-level DELEGATECALL with the given payload, returns success condition and return data, forwards all available gas, adjustable
* `<address>.staticcall(bytes memory) returns (bool, bytes memory)`: issue low-level STATICCALL with the given payload, returns success condition and return data, forwards all available gas, adjustable

### Contract-related keywords

* `this`: The current contract, explicitly convertible to Address
* `super`: A contract one level higher in the inheritance hierarchy
* `selfdestruct(address payable recipient)`: Destroy the current contract, sending its funds to the given Address and end execution. Note that selfdestruct has some peculiarities inherited from the EVM:
  * the receiving contract’s receive function is not executed.
  * the contract is only really destroyed at the end of the transaction and revert s might “undo” the destruction.


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