Bitcoin: error parsing json in bashscript to send BTC using sendmany command

Question

I am simulating a bitcoin network on my machine for which I have written a bash script to simulate the transactions between the nodes. When I use the sendmany option of bitcoin-cli to send transactions I am getting an json parsing error reported by bitcoin-cli.

Code:

#!/bin/bash
MAX_NODES=2
MY_PATH=/home/ubuntu/test
CLIENT=/usr/local/bin/bitcoin-cli

declare -a addr

function fcomp() {
        /usr/bin/awk -v n1=$1 -v n2=$2 'BEGIN{ if (n1>n2) exit 0; exit 1}'
}

json="'{"

#get addresses to send
for ((i = 1; i <= MAX_NODES; i++));
do
    addr[$i-1]="$($CLIENT -regtest -rpcport=$((16500 + $i)) -datadir=$MY_PATH/$i/ getnewaddress myaccount)"
    if [ "$i" -lt "$MAX_NODES" ]
    then
        json="$json\"${addr[$i-1]}\":0.00001, "
    else
        json="$json\"${addr[$i-1]}\":0.00001"
    fi
done

json="$json}'"
echo $json

#loop to send money to other nodes
for ((i = 1; i <= MAX_NODES; i++));
do
        balance=`$CLIENT -regtest -rpcport=$((16500 + $i)) -datadir=$MY_PATH/$i/ getbalance`
        if fcomp $balance 0.002; then
                $CLIENT -regtest -rpcport=$((16500 + $i)) -datadir=$MY_PATH/$i sendmany myaccount $json
    fi
done

echo json output:

'{"mj2FrDhEomSzyQtRoGY78oVRPcQs5L5o95":0.00001, "mkxnkT3kx9dsFS8V3qYydpL1o5F5MfwCvM":0.00001}'

This gives me an error as:

error: Error parsing JSON:'{"mj2FrDhEomSzyQtRoGY78oVRPcQs5L5o95":0.00001,

I tried all possible combinations of quotes, double quotes and escape sequences but failed. If I copy paste the output of echo $json to a manual bitcoin-cli sendmany command it works perfectly fine.

Answer 1

If this is your echo output:

'{"mj2FrDhEomSzyQtRoGY78oVRPcQs5L5o95":0.00001, "mkxnkT3kx9dsFS8V3qYydpL1o5F5MfwCvM":0.00001}'

Then you have too many quotes. When you run echo, you should see:

{"mj2FrDhEomSzyQtRoGY78oVRPcQs5L5o95":0.00001, "mkxnkT3kx9dsFS8V3qYydpL1o5F5MfwCvM":0.00001}

That's because the shell strips off the outer set of quotes; it does that when you send the JSON to bitcoin-cli too. Because you have the quotes there in the echo output, it implies that they're there in the bitcoin-cli command, so what you're sending Bitcoin Core looks like a JSON string rather than a JSON object.

---

This isn't asked in your question, but you might also want to look into the Debian/Ubuntu packages and commands named jshon and jq. These help you process JSON in shell scripts. Because they understand JSON, they tend to be a lot more robust the sed and awk. I don't know if you need them for this script, however.