Mastering Bitcoin, 3E (for True Epub) by Andreas M. Antonopoulos and David A. Harding

Author:Andreas M. Antonopoulos and David A. Harding
Language: eng
Format: epub
Publisher: O'Reilly Media, Inc.
Published: 2023-02-22T00:00:00+00:00

Bitcoin Core Application Programming Interface (API)

Bitcoin Core implements a JSON-RPC interface that can also be accessed using the command-line helper bitcoin-cli. The command line allows us to experiment interactively with the capabilities that are also available programmatically via the API. To start, invoke the help command to see a list of the available Bitcoin Core RPC commands:

$ bitcoin-cli help +== Blockchain == getbestblockhash getblock "blockhash" ( verbosity ) getblockchaininfo ... walletpassphrase "passphrase" timeout walletpassphrasechange "oldpassphrase" "newpassphrase" walletprocesspsbt "psbt" ( sign "sighashtype" bip32derivs finalize )

Each of these commands may take a number of parameters. To get additional help, a detailed description, and information on the parameters, add the command name after help. For example, to see help on the getblockhash RPC command:

$ bitcoin-cli help getblockhash getblockhash height Returns hash of block in best-block-chain at height provided. Arguments: 1. height (numeric, required) The height index Result: "hex" (string) The block hash Examples: > bitcoin-cli getblockhash 1000 > curl --user myusername --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "getblockhash", "params": [1000]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/

At the end of the help information you will see two examples of the RPC command, using the bitcoin-cli helper or the HTTP client curl. These examples demonstrate how you might call the command. Copy the first example and see the result:

$ bitcoin-cli getblockhash 1000 00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09

The result is a block hash, which is described in more detail in the following chapters. But for now, this command should return the same result on your system, demonstrating that your Bitcoin Core node is running, is accepting commands, and has information about block 1000 to return to you.

In the next sections we will demonstrate some very useful RPC commands and their expected output.

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