Creating the transaction

At this level, it's time to create a transaction that spends the received transaction. From the listunspent output, we have the necessary ingredients (prevout_hash and prevout_n) to construct our raw transaction. Let's see how.

First, you need to convert the hello world message into hexadecimal, using an online converter (such as https://codebeautify.org/string-hex-converter). The hexadecimal encoded form will be 68656c6c6f20776f726c64.

Then we have to use the createrawtransaction command, which creates a transaction spending the given inputs and creating new outputs. We have to pass as an argument (from the previous output) an object with the following parameters:

The txid of one of the available outputs
The vout index (prevout_n for Electrum) of the selected output
The hexadecimal form of the message
The destination address (created earlier)
The total number of satoshis (the smallest unit of the bitcoin currency) to send

Here we are sending one bitcoin, although you can set it to 0:

bitcoin-cli createrawtransaction "[{\"txid\":\"0791521362528725683caedf998006cf68b1cd817be1694ef0daca265d9b4252\", \"vout\": 1}]" "{\"data\":\"68656c6c6f20776f726c64\",\"2MsHsi4CHXsaNZSq5krnrpP4WShNgtuRa9U\":1.0000000}"

You'll get the following serialized long hex-encoded string, representing our raw transaction:

020000000152429b5d26cadaf04e69e17b81cdb168cf068099dfae3c6825875262135291070100000000ffffffff0200000000000000000d6a0b68656c6c6f20776f726c6400e1f5050000000017a914008051b4d96aa26269dfd36af0eb9c2b2fa894568700000000

To facilitate the usage of the previous CLI commands (and avoid manipulating long hex strings), you can assign the createrawtransaction output to a terminal variable, and use this later as an argument for the other commands. For example, we can use RAW=$ ( bitcoin-cli createrawtransaction .....). The resulting hexadecimal string will be stored in the RAW variable, and accessible using $RAW.

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