Block and Transaction Properties

• blockhash(uint blockNumber) returns (bytes32): hash of the given block - only works for 256 most recent, excluding current, blocks
• block.chainid (uint): current chain id
• block.coinbase (address payable): current block miner’s address
• block.difficulty (uint): current block difficulty
• 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 payable): 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 payable): sender of the transaction (full call chain)

Now let's learn how to use them

See the data types thet have been written inside the brackets near the pre-defined functions are the datatypes that is returned when called; not to confused with Arguments

Here are some examples how to use them

pragma solidity ^0.8.3;
contract Task2{
    

 // create a functions to return following things (chainid, blockhash, difficulty, gas limit, block number)
    
   // block.number(uint);
   function getBlockNumber()public view returns (uint){
          return block.number;
    }
    
    
   // blockhash(uint blockNumber) returns (bytes32);
   function getBlockHash() public view  returns (bytes32){
          return blockhash(getBlockNumber()); //Since here getBlockNumber() is defined before, so we used it
         //or simply write  return blockhash(block.number); 
    }
    
    
    //Block Hash of previous block
     function getPreviousBlockHash() public view  returns (bytes32){
          return blockhash(block.number-1);
    }
    
    
    // block.chainid (uint);
    function getChainId()public view returns (uint){
          return block.chainid;
    }
    
  
    // block.gaslimit (uint);
    function getGasLimit()public view returns (uint){
          return block.gaslimit;
    }
    
    // block.difficulty (uint);
    function getBlockDifficulty()public view returns (uint){
          return block.difficulty;
    }
   
  
}

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