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Update 4_2__Interlude_Using_JQ.md
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@ -164,14 +164,14 @@ You can of course rename your new keys as you see fit:
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The JQ lookups so far have been fairly simple: you use a key to lookup one or more key-values in a JSON Object or Array. But what if you instead want to lookup a key-value in an object ... by another key-value? This sort of indirect lookup has real applicability when you're working with transactions built on existing UTXOs. For example, what if you wanted to figure out the value of a UTXO we're using, something that we know is vitally important in raw transactions?
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To start with, we have a raw transaction:
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To start with, we have a raw transaction. Note that this is a more complex raw transaction with two inputs and two outputs. We'll learn about making those in a few sections, but for now it'll serve as an example of how to pluck all of the information out of a transaction:
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```
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$ bitcoin-cli decoderawtransaction $rawtxhex
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{
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"txid": "f445f121085d98635f7302e641f815d1ca4ce70f0e1b03f144ad1661dc5e10e7",
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"hash": "f445f121085d98635f7302e641f815d1ca4ce70f0e1b03f144ad1661dc5e10e7",
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"size": 85,
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"vsize": 85,
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"txid": "959190d447589e4c0f6ad31459579a4e4f6945b8791eadc9e5f0e55fc6205317",
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"hash": "959190d447589e4c0f6ad31459579a4e4f6945b8791eadc9e5f0e55fc6205317",
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"size": 160,
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"vsize": 160,
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"version": 2,
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"locktime": 0,
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"vin": [
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@ -183,11 +183,20 @@ $ bitcoin-cli decoderawtransaction $rawtxhex
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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": "ec0598918f6f5476cb90365651e8a2724ef26f949290bbf196f41ed96092a52f",
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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": 0.75950000,
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"value": 0.65050000,
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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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@ -198,21 +207,52 @@ $ bitcoin-cli decoderawtransaction $rawtxhex
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"n2eMqTT929pb1RDNuqEnxdaLau1rxy3efi"
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]
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}
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},
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{
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"value": 4.00000000,
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"n": 1,
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"scriptPubKey": {
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"asm": "OP_DUP OP_HASH160 29193095edbef6378fbcd84a8ae7c8164e433ca7 OP_EQUALVERIFY OP_CHECKSIG",
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"hex": "76a91429193095edbef6378fbcd84a8ae7c8164e433ca788ac",
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"reqSigs": 1,
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"type": "pubkeyhash",
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"addresses": [
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"mjGGB8rSXAHSd9xGA1bLfqMpB41XWuDdSF"
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]
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}
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}
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]
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}
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```
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[[SHOULD REALLY REDO THIS TO LIST ALL TRANSACTIONS, OR INCLUDE IT AS A SECOND EXAMPLE.]]
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To retrieve the 0th (and in this case only) txid, we need to `jq` to the .vin key-value, then to its 0th array, then to that array's .txid key-value. Easy:
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```
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$ usedtxid=$(bitcoin-cli decoderawtransaction $rawtxhex | jq -r '.vin | .[0] | .txid')
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$ echo $usedtxid
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### Retrieve the Value(s)
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If we wanted to just retrieve the txid for the two UTXOs, we need to `jq` to the .vin key-value, then to its 0th array, then to that array's .txid key-value. Then do the same with the 1st. Easy:
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```
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$ usedtxid1=$(bitcoin-cli decoderawtransaction $rawtxhex | jq -r '.vin | .[0] | .txid')
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$ echo $usedtxid1
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2b5f5798359e0e23e02764588166f222d4ce056419dec83c743b72aad171d708
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$ usedtxid2=$(bitcoin-cli decoderawtransaction $rawtxhex | jq -r '.vin | .[1] | .txid')
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$ echo $usedtxid2
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ec0598918f6f5476cb90365651e8a2724ef26f949290bbf196f41ed96092a52f
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```
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A magic invocation of `select` and `contains`, used after a typical pipe through all the JSON objects, can then be used to look up the transaction in question:
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However, it'd be better to have a general case that _automatically_ saved all the txids of our UTXOs. Fortunately, bash lets you nest a set of `()`s to put your output into an array. Here's an example
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```
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$ bitcoin-cli listunspent | jq -r '.[] | select (.txid | contains("'$usedtxid'"))'
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usedtxid=($(bitcoin-cli decoderawtransaction $rawtxhex | jq -r '.vin | .[] | .txid'))
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$ echo ${usedtxid[0]}
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2b5f5798359e0e23e02764588166f222d4ce056419dec83c743b72aad171d708
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$ echo ${usedtxid[1]}
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ec0598918f6f5476cb90365651e8a2724ef26f949290bbf196f41ed96092a52f
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```
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### Retrieve the Related Object(s)
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We can now step back to `listunspent`. To find our transactions, we need to look through the entire JSON Array (`[]`). We can then choose (`select`) individual JSON objects that include (`contain`) our txids. (The `select` and `contain` arguments show off some of the complexity of JSON, but for now just know that this particular invocation will work.)
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Here we are picking out our two UTXOs, one at a time:
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```
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$ bitcoin-cli listunspent | jq -r '.[] | select (.txid | contains("'${usedtxid[0]}'"))'
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{
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"txid": "2b5f5798359e0e23e02764588166f222d4ce056419dec83c743b72aad171d708",
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"vout": 1,
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@ -220,31 +260,86 @@ $ bitcoin-cli listunspent | jq -r '.[] | select (.txid | contains("'$usedtxid'")
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"account": "",
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"scriptPubKey": "76a9142fe70d51e886b9ef73b76c1743c5a2bb2894db8588ac",
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"amount": 0.76,
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"confirmations": 6617,
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"confirmations": 6689,
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"spendable": true,
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"solvable": true
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}
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$ bitcoin-cli listunspent | jq -r '.[] | select (.txid | contains("'${usedtxid[1]}'"))'
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{
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"txid": "ec0598918f6f5476cb90365651e8a2724ef26f949290bbf196f41ed96092a52f",
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"vout": 0,
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"address": "mjtEqr4Fffd1XtpAkKoDkMBP54mMXJeQ3j",
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"account": "",
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"scriptPubKey": "76a9142fe70d51e886b9ef73b76c1743c5a2bb2894db8588ac",
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"amount": 3.9,
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"confirmations": 7191,
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"spendable": true,
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"solvable": true
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}
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```
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Which leaves us with a wonderful two-line script to determine how much money was in the first UTXO input for a transaction:
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A simple Bash for-loop can instead give you _all_ of your UTXOs:
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```
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$ usedtxid=$(bitcoin-cli decoderawtransaction $rawtxhex | jq -r '.vin | .[0] | .txid')
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$ bitcoin-cli listunspent | jq -r '.[] | select (.txid | contains("'$usedtxid'")) | .amount'
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for txid in ${usedtxid[@]}; do bitcoin-cli listunspent | jq -r '.[] | select (.txid | contains("'$txid'"))'; done
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{
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"txid": "2b5f5798359e0e23e02764588166f222d4ce056419dec83c743b72aad171d708",
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"vout": 1,
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"address": "mjtEqr4Fffd1XtpAkKoDkMBP54mMXJeQ3j",
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"account": "",
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"scriptPubKey": "76a9142fe70d51e886b9ef73b76c1743c5a2bb2894db8588ac",
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"amount": 0.76,
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"confirmations": 6699,
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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": "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": 3.9,
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"confirmations": 7202,
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"spendable": true,
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"solvable": true
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}
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```
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## Use JSON for Simple Calculation by Key-Value
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**Usage Example:** _Automatically calculate the value of the UTXOs used in a transaction._
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You can now take one further step, and request the .amount (or any other JSON key-value) from the Objects you're retrieving:
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```
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$ usedtxid=($(bitcoin-cli decoderawtransaction $rawtxhex | jq -r '.vin | .[] | .txid'))
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$ for txid in ${usedtxid[@]}; do bitcoin-cli listunspent | jq -r '.[] | select (.txid | contains("'$txid'")) | .amount'; done
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0.76
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3.9
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```
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Using our earlier `awk` script, you can even add them up, to see how much money is in the UTXOs your transaction is spending:
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```
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$ usedtxid=($(bitcoin-cli decoderawtransaction $rawtxhex | jq -r '.vin | .[] | .txid'))
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$ for txid in ${usedtxid[@]}; do bitcoin-cli listunspent | jq -r '.[] | select (.txid | contains("'$txid'")) | .amount'; done | awk '{s+=$1} END {print s}'
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4.66
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```
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For more JSON magic (and if any of this isn't clear), please read the [JSON Manual](https://stedolan.github.io/jq/manual/) and the [JSON Cookbook](https://github.com/stedolan/jq/wiki/Cookbook).
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## Use JQ for Complex Calculations
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**Usage Example:** _Calculate the fee for a simple one-input, one-output transaction._
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**Usage Example:** _Calculate the fee for a real transaction._
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With this in hand, you can now use a few lines of code to see the transaction fee for the simple, one-input, one-output example raw transaction that we wrote in the previous section:
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```
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$ usedtxid=$(bitcoin-cli decoderawtransaction $rawtxhex | jq -r '.vin | .[0] | .txid')
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$ btcin=$(bitcoin-cli listunspent | jq -r '.[] | select (.txid | contains("'$usedtxid'")) | .amount')
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$ btcout=$(bitcoin-cli decoderawtransaction $rawtxhex | jq -r '.vout [0] | .value')
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$ usedtxid=($(bitcoin-cli decoderawtransaction $rawtxhex | jq -r '.vin | .[] | .txid'))
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$ btcin=$(for txid in ${usedtxid[@]}; do bitcoin-cli listunspent | jq -r '.[] | select (.txid | contains("'$txid'")) | .amount'; done | awk '{s+=$1} END {print s}')
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$ btcout=$(bitcoin-cli decoderawtransaction $rawtxhex | jq -r '.vout [] | .value' | awk '{s+=$1} END {print s}')
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$ echo "$btcin-$btcout"| /usr/bin/bc
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.0005
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.0095
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```
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And that's also a good example of why you double-check your fees: we'd intended to send a transaction fee of 5,000 satoshis, but sent 95,000 satoshis instead. Whoops!
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If you'd like to have this JQ
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> **WARNING:** This script has not been robustly checked. If you are going to use it to verify real transaction fees you should only do it as a triple-check after you've already done all the math yourself.
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### Use JQ to Calculate Transaction Fees for Real
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@ -254,5 +349,31 @@ However, as we've noted, a real transaction may have more than one input and wil
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> **WARNING:** This script has not been robustly checked. If you are going to use it to verify real transaction fees you should only do it as a triple-check after you've already done all the math yourself.
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```
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file: txfee-calc.sh
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#!/bin/bash
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if [ -z $1 ];
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then
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echo "You must include the raw transaction hex as an argument.";
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exit;
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fi
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usedtxid=($(bitcoin-cli decoderawtransaction $1 | jq -r '.vin | .[] | .txid'))
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btcin=$(for txid in ${usedtxid[@]}; do bitcoin-cli listunspent | jq -r '.[] | s
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elect (.txid | contains("'$txid'")) | .amount'; done | awk '{s+=$1} END {print
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s}')
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btcout=$(bitcoin-cli decoderawtransaction $1 | jq -r '.vout [] | .value' | awk
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'{s+=$1} END {print s}')
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echo "$btcin-$btcout"| /usr/bin/bc
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```
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You can then run it as follows:
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```
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$ ./txfee-calc.sh $rawtxhex
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.0095
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```
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## Make Some New Aliases
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