getblockhash height
Returns hash of block in best-block-chain at height provided.
Arguments:
1. height (numeric, required) The height index
Result:
"hex" (string) The block hash
Examples:
> bitcoin-cli getblockhash 1000
> curl --user myusername --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "getblockhash", "params": [1000]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/