4 - 5 自訂交易自動化

bitcoind 提供一個自動挑出 UTXO, 計算手續費的方法 fundrawtransaction

用法很簡單，先創造一個沒有 input 的交易，並指定要傳多少 BTC

$ unfinishedtx=$(bitcoin-cli -named createrawtransaction inputs='''[]''' outputs='''{"'$recipient'": 0.63 }''')

接者就可以用 fundrawtransaction 讓 bitcoind 自己挑

$ bitcoin-cli -named fundrawtransaction hexstring=$unfinishedtx
{
  "hex": "02000000013e6aa44b24cd9ccca813204fbb2dbaed5cda94722528aaff96bc0fa4e933189a0100000000feffffff02c04dc1030000000017a914a9974100aeee974a20cda9a2f545704a0ab54fdc87c0ea0e00000000001976a914ad7f3adbc38115d0ee68c8c2df06fd00604fabe088ac00000000",
  "changepos": 1,
  "fee": 0.00022400
}

我們一樣可以將交易的 hex 弄成變數，方便之後的使用

$ rawtxhex3=$(bitcoin-cli fundrawtransaction hexstring=$unfinishedtx | jq -r '.hex')

如果怕挑出來的會有問題，可以看看是不是正確

$ bitcoin-cli -named decoderawtransaction hexstring=$rawtxhex3
{
  "txid": "c217d4314b6d8965beac6235972188db4e4c9e13d78d126ade36b359f0e5858e",
  "hash": "c217d4314b6d8965beac6235972188db4e4c9e13d78d126ade36b359f0e5858e",
  "version": 2,
  "size": 117,
  "vsize": 117,
  "locktime": 0,
  "vin": [
    {
      "txid": "9a1833e9a40fbc96ffaa28257294da5cedba2dbb4f2013a8cc9ccd244ba46a3e",
      "vout": 1,
      "scriptSig": {
        "asm": "",
        "hex": ""
      },
      "sequence": 4294967294
    }
  ],
  "vout": [
    {
      "value": 0.00977600,
      "n": 0,
      "scriptPubKey": {
        "asm": "OP_DUP OP_HASH160 70d2a885d58edb1a3d0e7e06587687f69dfdb9ce OP_EQUALVERIFY OP_CHECKSIG",
        "hex": "76a91470d2a885d58edb1a3d0e7e06587687f69dfdb9ce88ac",
        "reqSigs": 1,
        "type": "pubkeyhash",
        "addresses": [
          "mqoWLLK3Z1kGEEGF94iPomFApAg4WcExVM"
        ]
      }
    },
    {
      "value": 0.63000000,
      "n": 1,
      "scriptPubKey": {
        "asm": "OP_HASH160 a9974100aeee974a20cda9a2f545704a0ab54fdc OP_EQUAL",
        "hex": "a914a9974100aeee974a20cda9a2f545704a0ab54fdc87",
        "reqSigs": 1,
        "type": "scripthash",
        "addresses": [
          "2N8hwP1WmJrFF5QWABn38y63uYLhnJYJYTF"
        ]
      }
    }
  ]
}

確認無誤就可以 signe & seal & deliver!