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https://github.com/ChristopherA/Learning-Bitcoin-from-the-Command-Line.git
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Update 3_Playing_with_Bitcoin.md
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Shannon Appelcline
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@ -650,7 +650,7 @@ In this case, we're going to spend the oldest transaction, because that's the on
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$ utxo_txid="ee9805676271f6244eba94c3d1a48b303a8f8359bf711c630eb6f2ea339d0e72"
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$ utxo_vout="0"
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```
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You should similarly record your recipient address, to make sure there are no problems:
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You should similarly record your recipient address, to make sure there are no problems. We're sending some money back to the TP faucet:
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```
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$ recipient="n2eMqTT929pb1RDNuqEnxdaLau1rxy3efi"
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```
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@ -682,7 +682,7 @@ $ bitcoin-cli createrawtransaction
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"'$your_recipient'": $your_amount
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}'''
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```
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Yeah, there's all kinds of crazy quotes there, but trust they'll do the right thing. Use `'''` to mark the start and end of the JSON array and object. Protect normal words like `"this"` and normal numbers like `0`. If they're variables, insert single quotes, like `"'$this_word'"` and `'$this_num'`. (Whew.)
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Yeah, there's all kinds of crazy quotes there, but trust they'll do the right thing. Use `'''` to mark the start and end of the JSON array and the JSON object. Protect normal words like `"this"` and normal numbers like `0`. If they're variables, insert single quotes, like `"'$this_word'"` and `'$this_num'`. (Whew. You'll get used to it.)
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Here's a command that sends creates a raw transaction to send our $utxo to our $recipient
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```
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@ -824,8 +824,276 @@ Congratulations! You're now a few satoshis poorer!
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### Create a Change Address
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Our first rawtransaction was very simplistic: we sent the entirety of a UTXO to a new address. More frequently, you'll want to send someone an amount of money that doesn't match a UTXO. But you'll recall that the excess money from a UTXO that's not sent to your recipient just becomes a transaction fee. So, how do you send someone just part of a UTXO, while keeping the rest for yourself (minus a transaction fee, of course)?
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The answer is that you create a change address:
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```
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$ changeaddress=$(bitcoin-cli getnewaddress)
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$ echo $changeaddress
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mxU9cmhJfkKWDtBspHaA36LkeafEDeaogJ
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```
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You now have an additional address inside your wallet that you can use to receive change from a UTXO!
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### Write a Raw Transacrion with Two Outputs
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You're now ready to write a more complex rawtransaction. It will be based on the two unspent UTXOs still in our wallet:
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```
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$ bitcoin-cli listunspent
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[
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{
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"txid": "c1abb6951e6a9aae7e384412b69b69e59c10daac9397d01d0c52b7bc6278d589",
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"vout": 1,
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"address": "mygxipnJUsBgFvscKAaoxDdE8aCmHhRfTZ",
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"account": "",
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"scriptPubKey": "76a914c756c7bd67bf83d83c04e3dc6fd1ff0c6fe8ea9888ac",
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"amount": 0.07800000,
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"confirmations": 237,
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"spendable": true,
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"solvable": true
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},
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{
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"txid": "ab7ca727055b812df882298f4e6e10ec699fb6250d843c813623171781f896d8",
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"vout": 0,
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"address": "mygxipnJUsBgFvscKAaoxDdE8aCmHhRfTZ",
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"account": "",
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"scriptPubKey": "76a914c756c7bd67bf83d83c04e3dc6fd1ff0c6fe8ea9888ac",
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"amount": 0.07800000,
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"confirmations": 237,
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"spendable": true,
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"solvable": true
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}
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]
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```
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We want to send 0.1 BTC back to the TP faucet. This requires combining our two UTXOs, because neither contains quite that amount of bitcoin. It also requires sending to two addresses: one for the TP faucet (n2eMqTT929pb1RDNuqEnxdaLau1rxy3efi) and one for a change address (mxU9cmhJfkKWDtBspHaA36LkeafEDeaogJ). In other words, we're going to have two inputs and two outputs in our raw transaction
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#### Set Up Your Variables
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We've already got `$changeaddress` and `$recipient` from our previous example:
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```
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$ echo $changeaddress
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mxU9cmhJfkKWDtBspHaA36LkeafEDeaogJ
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$ echo $recipient
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n2eMqTT929pb1RDNuqEnxdaLau1rxy3efi
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```
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We also need to record the txid and vout for each of our two UTXOs:
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```
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$ utxo_txid_1="c1abb6951e6a9aae7e384412b69b69e59c10daac9397d01d0c52b7bc6278d589"
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$ utxo_vout_1="1"
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$ utxo_txid_2="ab7ca727055b812df882298f4e6e10ec699fb6250d843c813623171781f896d8"
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$ utxo_vout_2="0"
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$ echo $utxo_txid_1
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c1abb6951e6a9aae7e384412b69b69e59c10daac9397d01d0c52b7bc6278d589
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$ echo $utxo_vout_1
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1
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$ echo $utxo_txid_2
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ab7ca727055b812df882298f4e6e10ec699fb6250d843c813623171781f896d8
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$ echo $utxo_vout_2
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0
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```
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#### Write the Transaction
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Writing the new raw transaction is surprisingly simple. All you need to do is include an additional, comma-separated JSON object in the JSON array of inputs and an additional, comma-separated key-value pair in the JSON object of outputs.
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Here's the example. Take a look at it carefully to understand where the inputs end the outputs begin:
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```
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rawtxhex2=$(bitcoin-cli createrawtransaction '''[ { "txid": "'$utxo_txid_1'", "vout": '$utxo_vout_1' }, { "txid": "'$utxo_txid_2'", "vout": '$utxo_vout_2' } ]''' '''{ "'$recipient'": 0.1, "'$changeaddress'": 0.0555 }''')
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```
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We were _very_ careful figuring out our money math. These two UTXOs contain .156 BTC. After sending .1 BTC, we'll have .056 BTC left. We again chose .0005 BTC for the transaction fee: this transaction is a little bigger, but that should still be enough to make this transaction go through quickly. To accomodate that, we set our change to .0555 BTC. If we'd messed up our math and instead set our change to .051 BTC, that additional .0045 BTC would be lost. That's $5 or $6 gone to the miners when it didn't need to. If we'd forgot to make change at all, then the whole .056 ($70!) would have disappeared. So, again, _be careful_.
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Back to the rawtransaction itself: we'll be honest, it took us a few times to get all the commas, quotes, and brackets in the right places, writing from the command line. We got JSON errors when we didn't format things quite right, and our variable got filled with the hex when we fixed those errors. So, as always, be careful here too, and check your work:
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```
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$ bitcoin-cli decoderawtransaction $rawtxhex2
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{
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"txid": "99b7454c20313806454f9fd4f3e0454ce93e6edd5e84dfc731bcc0ad352b2260",
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"hash": "99b7454c20313806454f9fd4f3e0454ce93e6edd5e84dfc731bcc0ad352b2260",
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"size": 160,
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"vsize": 160,
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"version": 1,
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"locktime": 0,
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"vin": [
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{
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"txid": "c1abb6951e6a9aae7e384412b69b69e59c10daac9397d01d0c52b7bc6278d589",
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"vout": 1,
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"scriptSig": {
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"asm": "",
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"hex": ""
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},
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"sequence": 4294967295
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},
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{
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"txid": "ab7ca727055b812df882298f4e6e10ec699fb6250d843c813623171781f896d8",
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"vout": 0,
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"scriptSig": {
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"asm": "",
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"hex": ""
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},
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"sequence": 4294967295
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}
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],
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"vout": [
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{
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"value": 0.10000000,
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"n": 0,
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"scriptPubKey": {
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"asm": "OP_DUP OP_HASH160 e7c1345fc8f87c68170b3aa798a956c2fe6a9eff OP_EQUALVERIFY OP_CHECKSIG",
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"hex": "76a914e7c1345fc8f87c68170b3aa798a956c2fe6a9eff88ac",
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"reqSigs": 1,
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"type": "pubkeyhash",
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"addresses": [
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"n2eMqTT929pb1RDNuqEnxdaLau1rxy3efi"
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]
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}
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},
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{
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"value": 0.05550000,
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"n": 1,
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"scriptPubKey": {
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"asm": "OP_DUP OP_HASH160 b9f2579814712f82a3dadfd73e0356339c6705b4 OP_EQUALVERIFY OP_CHECKSIG",
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"hex": "76a914b9f2579814712f82a3dadfd73e0356339c6705b488ac",
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"reqSigs": 1,
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"type": "pubkeyhash",
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"addresses": [
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"mxU9cmhJfkKWDtBspHaA36LkeafEDeaogJ"
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]
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}
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}
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]
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}
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```
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#### Finish It Up
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You can now sign, seal, and deliver your transaction, and it's yours (and the faucets):
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```
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$ bitcoin-cli signrawtransaction $rawtxhex2
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{
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"hex": "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",
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"complete": true
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}
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$ signedtx2="010000000289d57862bcb7520c1dd09793acda109ce5699bb61244387eae9a6a1e95b6abc1010000006a4730440220194cf452c76630419b90ef16bc9c0f31bd3187b97357eff6b610a3054968579b02200bcdb125ac182bda338c1a64d7887efd3e4eaf1a8e7f517eb7630d4dc258bf88012102f9006968b057f5212752964546d4c259f359601d00de32ec027fd84760bb4a46ffffffffd896f88117172336813c840d25b69f69ec106e4e8f2982f82d815b0527a77cab000000006a47304402201e65fe69dd231f73a9f493ca6c49503d51a766cf27be1281c9a4eefd04b4ac1c022003750d1ec93ef7be552aa55656c1860c986ef04a8733587f4f7be38707cccaf2012102f9006968b057f5212752964546d4c259f359601d00de32ec027fd84760bb4a46ffffffff0280969800000000001976a914e7c1345fc8f87c68170b3aa798a956c2fe6a9eff88acb0af5400000000001976a914b9f2579814712f82a3dadfd73e0356339c6705b488ac00000000"
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$ bitcoin-cli sendrawtransaction $signedtx2
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18f1a791e3f7735dbe1c92b86645ba9b1f62b8044f61efd76d082a084982c9ae
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```
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#### Wait
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As usual, your money will be in flux for a while. You used all of your UTXOs, so your `getbalance` may show that you have cash, but the transaction must be confirmed before you'll see a UTXO with your change.
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But, in 10 minutes or less (probably), you'll have your money back and fully spendable again:
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```
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$ bitcoin-cli listunspent
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[
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{
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"txid": "18f1a791e3f7735dbe1c92b86645ba9b1f62b8044f61efd76d082a084982c9ae",
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"vout": 1,
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"address": "mxU9cmhJfkKWDtBspHaA36LkeafEDeaogJ",
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"account": "",
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"scriptPubKey": "76a914b9f2579814712f82a3dadfd73e0356339c6705b488ac",
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"amount": 0.05550000,
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"confirmations": 2,
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"spendable": true,
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"solvable": true
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}
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]
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```
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### Optional: Write a Raw Transaction with Automatic Funding
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The purpose of this tutorial is to show you the very basics of Bitcoin scripting, so that you can work at things at a fundamental level. If you were writing a wallet or something other Bitcoin software, you'd probably want to do things exactly as described here. However, if you were for some reason regularly sending bitcoins about through rawtransactions created by hand, then you'd want to have a little better insurance that you weren't making mistakes.
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The bitcoin-cli accomodates this with a `fundrawtransaction` command. First, you have to make sure that your ~/.bitcoin/bitcoin.conf file has some rational variables for calculating transaction fees. We've been quite aggressive with fees in this tutorial, to make sure the examples finish quickly, but the following would allow for cheaper transmissions that might take a few hours:
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```
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paytxfee=0.0001
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mintxfee=0.0001
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txconfirmtarget=25
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```
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With that in hand you create `createrawtransaction` with just your output(s), then run `fundrawtransaction` on the resulting hex:
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```
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$ unfinishedtx=$(bitcoin-cli createrawtransaction '''[]''' '''{ "'$recipient'": 0.04 }''')
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$ bitcoin-cli fundrawtransaction $unfinishedtx
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{
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"hex": "0100000001aec98249082a086dd7ef614f04b8621f9bba4566b8921cbe5d73f7e391a7f1180100000000feffffff0208951700000000001976a914f26e11dc0fcc79fe76fca1d24d7588798922ca7488ac00093d00000000001976a914e7c1345fc8f87c68170b3aa798a956c2fe6a9eff88ac00000000",
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"changepos": 0,
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"fee": 0.00004520
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}
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rawtxhex3="0100000001aec98249082a086dd7ef614f04b8621f9bba4566b8921cbe5d73f7e391a7f1180100000000feffffff0208951700000000001976a914f26e11dc0fcc79fe76fca1d24d7588798922ca7488ac00093d00000000001976a914e7c1345fc8f87c68170b3aa798a956c2fe6a9eff88ac00000000"
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```
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You'll of course want to check the output:
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```
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$ bitcoin-cli decoderawtransaction $rawtxhex3
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{
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"txid": "3099716446e0761e823077fc2f33c158b1dbaa7c157cb03c25a7cf6b7ac4921d",
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"hash": "3099716446e0761e823077fc2f33c158b1dbaa7c157cb03c25a7cf6b7ac4921d",
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"size": 119,
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"vsize": 119,
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"version": 1,
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"locktime": 0,
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"vin": [
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{
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"txid": "18f1a791e3f7735dbe1c92b86645ba9b1f62b8044f61efd76d082a084982c9ae",
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"vout": 1,
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"scriptSig": {
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"asm": "",
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"hex": ""
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},
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"sequence": 4294967294
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}
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],
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"vout": [
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{
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"value": 0.01545480,
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"n": 0,
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"scriptPubKey": {
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"asm": "OP_DUP OP_HASH160 f26e11dc0fcc79fe76fca1d24d7588798922ca74 OP_EQUALVERIFY OP_CHECKSIG",
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"hex": "76a914f26e11dc0fcc79fe76fca1d24d7588798922ca7488ac",
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"reqSigs": 1,
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"type": "pubkeyhash",
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"addresses": [
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"n3cogFw4y3A1LJgRz2G97otEGT7BK8ca3D"
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]
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}
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},
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{
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"value": 0.04000000,
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"n": 1,
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"scriptPubKey": {
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"asm": "OP_DUP OP_HASH160 e7c1345fc8f87c68170b3aa798a956c2fe6a9eff OP_EQUALVERIFY OP_CHECKSIG",
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"hex": "76a914e7c1345fc8f87c68170b3aa798a956c2fe6a9eff88ac",
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"reqSigs": 1,
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"type": "pubkeyhash",
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"addresses": [
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"n2eMqTT929pb1RDNuqEnxdaLau1rxy3efi"
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]
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}
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}
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]
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}
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```
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As you can see, it chose UTXOs for the inputs, it created a change address, it calculated a (low) transaction fee based on the variables in the bitcoin.conf file, and it send the amount of the UTXO minus the tx fee back.
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You can even verify that the new address belongs to you:
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```
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$ bitcoin-cli validateaddress n3cogFw4y3A1LJgRz2G97otEGT7BK8ca3D
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{
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"isvalid": true,
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"address": "n3cogFw4y3A1LJgRz2G97otEGT7BK8ca3D",
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"scriptPubKey": "76a914f26e11dc0fcc79fe76fca1d24d7588798922ca7488ac",
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"ismine": true,
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"iswatchonly": false,
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"isscript": false,
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"pubkey": "0347251fdd4fe8f9c66c0c137cc641e864dd27fc5dc0c8d0c85ff884d2a3fa1574",
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"iscompressed": true,
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"hdkeypath": "m/0'/0'/4'",
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"hdmasterkeyid": "75807dcb1226537ceb54c38c4a75a61407fdd02d"
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}
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```
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At this point you could sign and send the transaction as usual ... then wait much longer for it to come back due to the lower transaction fees!
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```
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$ signedtx3="0100000001aec98249082a086dd7ef614f04b8621f9bba4566b8921cbe5d73f7e391a7f118010000006b483045022100a9b1454114bb2c04b51619eb5a00ad391605920ae801405b6191a64d1fb1e6e8022054def9ccbd75cb7929279cfef73ac573cdac7a325a1e3c8f43e139a1340b5d4b012103f7c794378db1c070b07d74f427f394f8a5d53f1abe1d2dab100d5a7a49db8785feffffff0208951700000000001976a914f26e11dc0fcc79fe76fca1d24d7588798922ca7488ac00093d00000000001976a914e7c1345fc8f87c68170b3aa798a956c2fe6a9eff88ac00000000"
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$ bitcoin-cli sendrawtransaction $signedtx3
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ecfc625fff594683e90d21618b64f44f7046c55bcda6468c1c37c1abe8b83913
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```
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We will _not_ be using this technique in the rest of the tutorial.
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### Write a Raw Transaction with an OP_RETURN
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Saving Data on the blockchain
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Loading…
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