With bitcoin-core, you get a configuration option called walletnotify which allow you to invoke a command whenever you receive a payment, first confirmation of a payment or send a payment.

You can specify %s as an argument which will be used to parse the transaction id.

Bitcoind WalletNotify TransactionID Example

To see what walletnotify does, in my bitcoin.conf I had a basic script to write a entry every time I receive a payment:

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$ cat ~/.bitcoin/bitcoin.conf
...
walletnotify=/bin/notify.sh %s %w

And in my /bin/notify.sh script I have this:

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#!/usr/bin/env bash
transaction_id=$1

# writing to log
echo "[$(date +%FT%T)] event for txid $transaction_id" >> /var/log/bitcoin-notify.log

I have executable permissions for the script:

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$ chmod +x /bin/notify.sh

When a payment was made, my logfile showed the following:

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[2021-08-04T12:21:43] event for txid xxxxxx5d92f729ed77xxxxxx2cbccedxxxxa7a03a801xxxxxxx33a41c1xxxxxd2 

Capturing the wallet name in walletnotify

In bitcoin-core we wave wallets, and in a wallet we have one or more bitcoin addresses, as can be seen below for wallets:

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$ curl -s -u "bitcoin:${bpass}" -d '{"jsonrpc": "1.0", "id": "curl", "method": "listwallets", "params": []}' -H 'content-type: text/plain;' http://127.0.0.1:18332/
{"result":["rpi01-main", "rpi01-secondary"],"error":null,"id":"curl"}

and to get the addresses for that wallet:

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$ curl -s -u "bitcoin:${bpass}" -d '{"jsonrpc": "1.0", "id": "curl", "method": "getaddressesbylabel", "params": [""]}' -H 'content-type: text/plain;' http://127.0.0.1:18332/wallet/rpi01-main
{"result":{"txxxxxmefmcpq98xxxxxxx80gvug2fe97xxxxxx8yv":{"purpose":"receive"}},"error":null,"id":"curl"}

I had to figure out how to capture the wallet name as well as the transaction id, as I thought its not possible until I stumbled upon a post which mentioned from bitcoind 0.20:

The -walletnotify configuration parameter will now replace any %w in its argument with the name of the wallet generating the notification.

Which was merged by this PR: - https://github.com/bitcoin/bitcoin/pull/13339

So first to verify that bitcoind is newer than mentioned:

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$ /usr/local/bin/bitcoind -version
Bitcoin Core version v0.21.1

Updated the walletnotify config in bitcoin.conf to include %w:

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$ cat /home/bitcoin/.bitcoin/bitcoin.conf | grep wallet
walletnotify=/bin/notify.sh %s %w

Then in the notify.sh script:

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#!/usr/bin/env bash
transaction_id=$1
wallet_name=$2

echo "[$(date +%FT%T)] $transaction_id $wallet_name" >> /var/log/bitcoin-notify.log

And then restart bitcoind:

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$ sudo systemctl restart bitcoind

When a transaction occurred, I could see the transaction id with the corresponding wallet name:

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$ tail -f /var/log/bitcoin-notify.log
[2021-08-04T12:31:20] fxxxxxxxxxxxxxxxxxxxxxxx2cbcced28ea26fhkxxxxhjn01f33a41c12f8xxx8 rpi01-main

Thanks

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