Returns the height of the most-work fully-validated chain. The genesis block has height 0.
curl --user myuser --data-binary '{"jsonrpc":"1.0","id":"1","method":"getblockcount","params":[]}' -H 'content-type:text/plain;' http://127.0.0.1:8332/
840000
getblockchaininfo
getblockfilter
bitcoind.app — Bitcoin Core RPC Reference