Say you want to get a block hash and you only know the block height, you can use the getblockhash to get the hash of the block.

getblockhash query commands only take one argument which is the height of the block.

Let’s get the hash of block 800,000.

bitcoin-cli getblockhash 800000

Result:

00000000000000000002a7c4c1e48d76c5a37902165a270156b7a8d72728a054

You can use this block hash to get the block data.