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Update 4_2__Interlude_Using_JQ.md

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Shannon Appelcline 2017-03-29 15:02:02 -07:00 committed by GitHub
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4_2__Interlude_Using_JQ.md
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@ -326,7 +326,7 @@ $ for txid in ${usedtxid[@]}; do bitcoin-cli listunspent | jq -r '.[] | select (
**Usage Example:** _Calculate the fee for a real transaction._
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:
A few more lines of code which add out the values of your vout, then subtract your vout from your vin can be used to calculate your transaction fee:
```
$ usedtxid=($(bitcoin-cli decoderawtransaction $rawtxhex | jq -r '.vin | .[] | .txid'))
$ btcin=$(for txid in ${usedtxid[@]}; do bitcoin-cli listunspent | jq -r '.[] | select (.txid | contains("'$txid'")) | .amount'; done | awk '{s+=$1} END {print s}')
@ -336,6 +336,8 @@ $ echo "$btcin-$btcout"| /usr/bin/bc
```
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!
> **WARNING:** This was not a clever little lesson. We messed up our calculation of the the transaction fee when we wrote our raw transaction. It's *that* easy, then your money is gone.
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). We'll be regularly using JQ in future examples.
### The Transaction Fee Script
@ -364,7 +366,7 @@ btcout=$(bitcoin-cli decoderawtransaction $1 | jq -r '.vout [] | .value' | awk
echo "$btcin-$btcout"| /usr/bin/bc
```
You can then run it as follows:
You can then run the script as follows:
```
$ ./txfee-calc.sh $rawtxhex
.0095