获取最新区块号

$ cast block-number --help

用法：cast block-number [OPTIONS] [BLOCK]

参数：
  [BLOCK]
          The hash or tag to query. If not specified, the latest number is
          returned

选项：
  -r, --rpc-url <URL>
          The RPC endpoint
          
          [env: ETH_RPC_URL=]

      --flashbots
          Use the Flashbots RPC URL with fast mode
          (<https://rpc.flashbots.net/fast>).
          
          This shares the transaction privately with all registered builders.
          
          See:
          <https://docs.flashbots.net/flashbots-protect/quick-start#faster-transactions>

      --jwt-secret <JWT_SECRET>
          JWT Secret for the RPC endpoint.
          
          The JWT secret will be used to create a JWT for a RPC. For example,
          the following can be used to simulate a CL `engine_forkchoiceUpdated`
          call:
          
          cast rpc --jwt-secret <JWT_SECRET> engine_forkchoiceUpdatedV2
          '["0x6bb38c26db65749ab6e472080a3d20a2f35776494e72016d1e339593f21c59bc",
          "0x6bb38c26db65749ab6e472080a3d20a2f35776494e72016d1e339593f21c59bc",
          "0x6bb38c26db65749ab6e472080a3d20a2f35776494e72016d1e339593f21c59bc"]'
          
          [env: ETH_RPC_JWT_SECRET=]

  -h, --help
          Print help (see a summary with '-h')