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updating examples
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Shannon Appelcline
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@ -8,13 +8,13 @@ We can now put those together and actually send funds using a raw transaction.
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## Create a Change Address
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Our sample raw transaction in section 4.2 was very simplistic: we sent the entirety of a UTXO to a new address. More frequently, you'll want to send someone an amount of money that doesn't match a UTXO. But, you'll recall that the excess money from a UTXO that's not sent to your recipient just becomes a transaction fee. So, how do you send someone just part of a UTXO, while keeping the rest for yourself?
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Our sample raw transaction in section §4.2 was very simplistic: we sent the entirety of a UTXO to a new address. More frequently, you'll want to send someone an amount of money that doesn't match a UTXO. But, you'll recall that the excess money from a UTXO that's not sent to your recipient just becomes a transaction fee. So, how do you send someone just part of a UTXO, while keeping the rest for yourself?
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The solution is to _send_ the rest of the funds to a second address, a change address that you've created in your wallet specifically to receive them:
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```
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$ changeaddress=$(bitcoin-cli getrawchangeaddress)
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$ changeaddress=$(bitcoin-cli getrawchangeaddress legacy)
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$ echo $changeaddress
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myrK8U3SE1nWh9y9XPho5aTrKYW6n8qSQv
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mk9ry5VVy8mrA8SygxSQQUDNSSXyGFot6h
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```
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Note that this uses a new function: `getrawchangeaddress`. It's largely the same as `getnewaddress` but is optimized for use as a change address in a raw transaction, so it doesn't do things like make entries in your address book.
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@ -28,52 +28,70 @@ Our sample raw transaction was simple in another way: it assumed that there was
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To summarize: creating a real raw transaction to send coins will sometimes require multiple inputs and will almost always require multiple outputs, one of which is a change address. We'll be creating that sort of more realistic transaction here, in a new example that shows a real-life example of sending funds via Bitcoin's second methodology, raw transactions.
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Here's the UTXOs we'll be using:
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We're going to use our 0th and 2nd UTXOs:
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```
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$ bitcoin-cli listunspent
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[
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[
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{
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"txid": "ec0598918f6f5476cb90365651e8a2724ef26f949290bbf196f41ed96092a52f",
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"vout": 0,
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"address": "mjtEqr4Fffd1XtpAkKoDkMBP54mMXJeQ3j",
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"account": "",
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"scriptPubKey": "76a9142fe70d51e886b9ef73b76c1743c5a2bb2894db8588ac",
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"amount": 3.90000000,
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"confirmations": 9551,
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"txid": "0619fecf6b2668fab1308fbd7b291ac210932602a6ac6b8cc11c7ae22c43701e",
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"vout": 1,
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"address": "mwJL7cRiW2bUnY81r1thSu3D4jtMmwyU6d",
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"label": "",
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"scriptPubKey": "76a914ad1ed1c5971b2308f89c1362d4705d020a40e8e788ac",
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"amount": 0.00899999,
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"confirmations": 1,
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"spendable": true,
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"solvable": true
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"solvable": true,
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"desc": "pkh([d6043800/0'/0'/4']03eae28c93035f95a620dd96e1822f2a96e0357263fa1f87606a5254d5b9e6698f)#wwnfx2sp",
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"safe": true
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},
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{
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"txid": "3470e5fe08633583d136b9cd49bb1a224c9d9313a0b4584fd3b7438dbdf34dbd",
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"txid": "91261eafae15ea53dedbea7c1db748c52bbc04a85859ffd0d839bda1421fda4c",
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"vout": 0,
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"address": "msiyutru5TV33Q2UGK2Bbh2ewdrYALBzTb",
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"account": "",
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"scriptPubKey": "76a91485e7d9fe99708d575f3b93be13c0c55c6ffb765088ac",
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"amount": 1.95000000,
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"confirmations": 9542,
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"address": "mjehC2KHzXcBDcwTd4LhZ2GzyzrZ3Kd3ff",
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"label": "",
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"scriptPubKey": "76a9142d573900aa357a38afd741fbf24b075d263ea6e088ac",
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"amount": 0.00022000,
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"confirmations": 15,
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"spendable": true,
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"solvable": true
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}
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"solvable": true,
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"desc": "pkh([d6043800/0'/0'/3']0278608b54b8fb0d8379d3823d31f03a7c6ab0adffb07dd3811819fdfc34f8c132)#nhjc3f8y",
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"safe": true
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},
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{
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"txid": "0df23a9dba49e822bbc558f15516f33021a64a5c2e48962cec541e0bcc79854d",
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"vout": 0,
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"address": "mwJL7cRiW2bUnY81r1thSu3D4jtMmwyU6d",
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"label": "",
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"scriptPubKey": "76a914ad1ed1c5971b2308f89c1362d4705d020a40e8e788ac",
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"amount": 0.00100000,
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"confirmations": 1,
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"spendable": true,
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"solvable": true,
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"desc": "pkh([d6043800/0'/0'/4']03eae28c93035f95a620dd96e1822f2a96e0357263fa1f87606a5254d5b9e6698f)#wwnfx2sp",
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"safe": true
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}
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]
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```
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In our example, we're going to send 4.0 BTC, which is larger than either of our UTXOs. This requires combining them, then using our change address to retrieve the unspent funds.
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In our example, we're going to send .009 BTC, which is (barely) larger than either of our UTXOs. This requires combining them, then using our change address to retrieve the unspent funds.
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### Set Up Your Variables
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We already have `$changeaddress` and `$recipient` variables from previous examples:
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```
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$ echo $changeaddress
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myrK8U3SE1nWh9y9XPho5aTrKYW6n8qSQv
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~$ echo $recipient
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mk9ry5VVy8mrA8SygxSQQUDNSSXyGFot6h
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$ echo $recipient
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n2eMqTT929pb1RDNuqEnxdaLau1rxy3efi
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```
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We also need to record the txid and vout for each of our two UTXOs. Having identified the UTXOs that we want to spend, we can use our JQ techniques to make sure accessing them is error free:
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```
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$ utxo_txid_1=$(bitcoin-cli listunspent | jq -r '.[0] | .txid')
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$ utxo_vout_1=$(bitcoin-cli listunspent | jq -r '.[0] | .vout')
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$ utxo_txid_2=$(bitcoin-cli listunspent | jq -r '.[1] | .txid')
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$ utxo_vout_2=$(bitcoin-cli listunspent | jq -r '.[1] | .vout')
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$ utxo_txid_2=$(bitcoin-cli listunspent | jq -r '.[2] | .txid')
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$ utxo_vout_2=$(bitcoin-cli listunspent | jq -r '.[2] | .vout')
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```
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### Write the Transaction
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@ -82,14 +100,14 @@ Writing the actual raw transaction is surprisingly simple. All you need to do is
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Here's the example. Note the multiple inputs after the `inputs` arg and the multiple outputs after the `outputs` arg.
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```
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$ rawtxhex2=$(bitcoin-cli -named createrawtransaction inputs='''[ { "txid": "'$utxo_txid_1'", "vout": '$utxo_vout_1' }, { "txid": "'$utxo_txid_2'", "vout": '$utxo_vout_2' } ]''' outputs='''{ "'$recipient'": 4.0, "'$changeaddress'": 1.8495 }''')
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$ $ rawtxhex2=$(bitcoin-cli -named createrawtransaction inputs='''[ { "txid": "'$utxo_txid_1'", "vout": '$utxo_vout_1' }, { "txid": "'$utxo_txid_2'", "vout": '$utxo_vout_2' } ]''' outputs='''{ "'$recipient'": 0.009, "'$changeaddress'": 0.0009 }''')
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```
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We were _very_ careful figuring out our money math. These two UTXOs contain 5.85 BTC. After sending 4.0 BTC, we'll have 1.85 BTC left. We again chose .0005 BTC for the transaction fee. To accommodate that fee, we set our change to 1.8495 BTC. If we'd messed up our math and instead set our change to 1.7495 BTC, that additional .1 BTC would be lost. That's $100 gone to the miners! If we'd forgot to make change at all, then the whole 1.85 BTC ($2000!) would have disappeared. So, again, _be careful_.
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We were _very_ careful figuring out our money math. These two UTXOs contain 5.85 BTC. After sending 0.009 BTC, we'll have .00099999 BTC left. We chose .00009999 BTC the transaction fee. To accommodate that fee, we set our change to .0009 BTC. If we'd messed up our math and instead set our change to .00009 BTC, that additional BTC would be lost to the miners! If we'd forgot to make change at all, then the whole excess would have disappeared. So, again, _be careful_.
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Fortunately, we can triple-check with the `btctxfee` alias from the JQ Interlude:
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```
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$ btctxfee $rawtxhex2
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.0005
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$ ./txfee-calc.sh $rawtxhex2
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.00009999
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```
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### Finish It Up
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@ -98,31 +116,34 @@ You can now sign, seal, and deliver your transaction, and it's yours (and the fa
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```
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$ signedtx2=$(bitcoin-cli -named signrawtransactionwithwallet hexstring=$rawtxhex2 | jq -r '.hex')
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$ bitcoin-cli -named sendrawtransaction hexstring=$signedtx2
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69c9ef4d1adb48596c470146ee9b60593023b6eb870b79ef666a8c9369768469
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e7071092dee0b2ae584bf6c1ee3c22164304e3a17feea7a32c22db5603cd6a0d
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```
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### Wait
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As usual, your money will be in flux for a while: the change will be unavailable until the transaction actually gets confirmed and a new UTXO is given to you.
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But, in 10 minutes or less (probably), you'll have your remaining money back and fully spendable again:
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But, in 10 minutes or less (probably), you'll have your remaining money back and fully spendable again. For now, we're still waiting:
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```
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$ bitcoin-cli listunspent
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[
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{
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"txid": "69c9ef4d1adb48596c470146ee9b60593023b6eb870b79ef666a8c9369768469",
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"vout": 1,
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"address": "myrK8U3SE1nWh9y9XPho5aTrKYW6n8qSQv",
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"scriptPubKey": "76a914c91b8f2f983aa9f8f0ba552adf6b6491ac01e02888ac",
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"amount": 1.84950000,
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"confirmations": 2,
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"txid": "91261eafae15ea53dedbea7c1db748c52bbc04a85859ffd0d839bda1421fda4c",
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"vout": 0,
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"address": "mjehC2KHzXcBDcwTd4LhZ2GzyzrZ3Kd3ff",
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"label": "",
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"scriptPubKey": "76a9142d573900aa357a38afd741fbf24b075d263ea6e088ac",
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"amount": 0.00022000,
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"confirmations": 15,
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"spendable": true,
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"solvable": true
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"solvable": true,
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"desc": "pkh([d6043800/0'/0'/3']0278608b54b8fb0d8379d3823d31f03a7c6ab0adffb07dd3811819fdfc34f8c132)#nhjc3f8y",
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"safe": true
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}
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]
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```
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This also might be a good time to revisit a blockchain explorer, so that you can see more intuitively how the inputs, outputs, and transaction fee are all laid out: [69c9ef4d1adb48596c470146ee9b60593023b6eb870b79ef666a8c9369768469](https://live.blockcypher.com/btc-testnet/tx/69c9ef4d1adb48596c470146ee9b60593023b6eb870b79ef666a8c9369768469/).
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This also might be a good time to revisit a blockchain explorer, so that you can see more intuitively how the inputs, outputs, and transaction fee are all laid out: [e7071092dee0b2ae584bf6c1ee3c22164304e3a17feea7a32c22db5603cd6a0d](https://live.blockcypher.com/btc-testnet/tx/e7071092dee0b2ae584bf6c1ee3c22164304e3a17feea7a32c22db5603cd6a0d/).
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## Summary: Sending Coins with Raw Transactions
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