Is there a way to find the coinbase for a given block using only bitcoind commands?


Update August 7 2015 ~ start

So after having an IP or two banned because of checking to often... so, I'll provide some options on how to avoid getting banned. First don't use the script under this update; the variable expansion Bash preforms causes multiple calls to in to short of a time frame. You can try adding sleep 120 between the assignment and calls but that would be very slow. Second the key things are; Checking local count $(bitcoin-cli getblockcount) and Checking a well known node $(wget -q -O - and Checking local sync state $(bitcoin-cli getblocktemplate)

To combine the Blockchain from your node to another in one line

$($(wget -q -O -$(bitcoin-cli getblockcount)) # To print this with echo and date stamp echo " $(date) : $($(wget -q -O -$(bitcoin-cli getblockcount))" # To redirect and exit with 0 : ie place in...
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Find examples of how to build programs using Bitcoin.

The following guide aims to provide examples to help you start building Bitcoin-based applications. To make the best use of this document, you may want to install the current version of Bitcoin Core, either from source or from a pre-compiled executable.

Once installed, you’ll have access to three programs: bitcoind, bitcoin-qt, and bitcoin-cli.

bitcoin-qt provides a combination full Bitcoin peer and wallet frontend. From the Help menu, you can access a console where you can enter the RPC commands used throughout this document.

bitcoind is more useful for programming: it provides a full peer which you can interact with through RPCs to port 8332 (or 18332 for testnet).

bitcoin-cli allows you to send RPC commands to bitcoind from the command line. For example, bitcoin-cli help

All three programs get settings from bitcoin.conf in the Bitcoin application...

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0-Confirmation (Zero-Confirmation)

See Unconfirmed Transaction and Confirmation Number.

51% Attack

Also known as >50% attack or a double spend attack. An attacker can make a payment, wait till the merchant accepts some number of confirmations and provides the service, then starts mining a parallel chain of blocks starting with a block before the transaction. This parallel blockchain then includes another transaction that spends the same outputs on some other address. When the parallel chain becomes more difficult, it is considered a main chain by all nodes and the original transaction becomes invalid. Having more than a half of total hashrate guarantees possibility to overtake chain of any length, hence the name of an attack (strictly speaking, it is "more than 50%", not 51%). Also, even 40% of hashrate allows making a double spend, but the chances are less than 100% and are diminishing exponentially with the number of confirmations that the merchant requires. This attack is...

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Actually, yes.
Transactions sent on the networks are broadcast across the network instantly. This is why when someone sends you a Bitcoin payment to your Coinbase account, you can see it show up as "pending" right away. Other wallets and some Bitcoin clients can accept these 0 confirmation transactions.

The Coinbase wallet will wait until a transaction has 3 confirmations before marking it as "complete." Other wallets and services will wait for more or less confirmations. There is no arbitrary amount that Bitcoin says you have to follow. But the general rule is: the more confirmations a transaction has, the "safer" it is to accept it. I'm going to go way off on a tangent and get a bit technical, but here's one reason why:


Miners (and probably more specifically, mining pools) are the entities in Bitcoin that submit blocks and confirm the transactions. But what happens if two miners submit a block at the same time? This happens more than you...

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Chapter 4

Frequently Asked Questions

If you're still a bit confused, that's okay. Buying bitcoins is hard and that's why I built this site.

If you don't find an answer to your question in the section below, then post in our Ask section and I'll answer within 24 hours.

What risks are involved when buying bitcoins with credit card?

First of all, make sure the company you're buying for has a good reputation and is regulated. It's possible that sketchy companies selling bitcoins may be collecting CC information and could possibly scam you later.

Some users have reported cash advanced fees, so be sure to understand how your CC company handles the purchase of bitcoins.

What are the benefits and advantages?

It can be easy to get bitcoins fast if purchasing with a debit/credit card. Since most people understand how to shop online using credit and debit cards, it may be easier for less technical buyers to use credit cards to...

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This post is a reference for Bitcoin Core version 0.9.3

Configuring Bitcoin-RPC

Prior to 0.9.0 there were a number of commands you could give bitcoind from the command line. Those commands exposed the features required for Bitcoin (sending payments, managing your wallet, etc). These commands were also available through a JSON-RPC api. The JSON-RPC interface better fit the model that most server processes follow.

Starting with bitcoind version 0.9.0, the command line interface was stripped out into a separate process called bitcoin-cli. All bitcoin-cli does is allow you to talk to the bitcoind JSON-RPC api from the command line. When debugging, you'll want to be able to use bitcoin-cli to send commands to the bitcoind running process. Of course it follows that in order for this to work you need to properly setup RPC in bitcoind. This is done through the bitcoin.conf file. Relevant settings from bitcoin.conf:

server=1 rpcuser=bitcoinrpc...
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746 posts

Hi @ur-86: you can disable it by running the "launcher.exe" together with the command line switch, as is mentioned below, but please be aware that you use it on your own risk:
- "Although not recommended, you can also use the command line flag --allow-running-insecure-content to prevent Chrome from checking for insecure content." - the source link,
- "Note: I don't approve that you do this, but you have asked for this, hence I'm providing you with a way to do it", "The permanent answer is to fix the offending website." - the source link.

In conclusion, the final note to consider, why you should not to do that - let me to cite the reply by Daniel Aleksandersen:
"Please contact the sites you see this alert on and ask them to fix their sites. The warning is there because the page author failed to take care of their own security." - the source link.


1644 posts

I believe...

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I think this is best answered by an example. Let's find the coinbase from a block on the Bitcoin testnet.

First we'll get the hash for a block we want to look at. We'll have a look at the (as I write this) latest block:

> bitcoind getblockcount 81626 > bitcoind getblockhash 81626 0000000000834f3933b50577b854692ed246728a17d10006ced1283a3fd8074c

Now we need to find the hash of the generation transaction from that block. It's always the first one listed. In this example there is only 1 transaction.

> bitcoind getblock 0000000000834f3933b50577b854692ed246728a17d10006ced1283a3fd8074c [...] "tx" : [ "f1fdeb7ced28f697c97b6a3ed7cc1946e1fc5e062ad8c17d05c88b1767b91b2a" ], [...]

And now we can grab the coinbase from the transaction. The getrawtransaction command's second parameter can be set to 1 to give us individual pieces of the transaction so we can easily find the coinbase. Alternatively we could leave that out and it would give us a single binary blob to...

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Blocks with a version of 2 or greater are required to put their block height in the coinbase. Your example doesn't. (At some point in the future, version 1 blocks will probably be discouraged and then banned.)

Here's an example of one that does:


The block height is the first thing in the coinbase. 03 is how many bytes the number has. So the number is 0x823203 in Bitcoin's little endian byte ordering, or 0x033282 in the big-endian byte ordering that humans usually use. Convert this into decimal and you can see that this is block...

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Bitcoin is a decentralized digital currency that enables instant payments to anyone, anywhere in the world. Bitcoin uses peer-to-peer technology to operate with no central authority: transaction management and money issuance are carried out collectively by the network.

The original Bitcoin software by Satoshi Nakamoto was released under the MIT license. Most client software, derived or "from scratch", also use open source licensing.

Bitcoin is the first successful implementation of a distributed crypto-currency, described in part in 1998 by Wei Dai on the cypherpunks mailing list. Building upon the notion that money is any object, or any sort of record, accepted as payment for goods and services and repayment of debts in a given country or socio-economic context, Bitcoin is designed around the idea of using cryptography to control the creation and transfer of money, rather than relying on central...

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The getutxo command allows querying of the UTXO set given a set of of outpoints. It has a simple implementation and the results are not authenticated in any way. Despite this, there are times when it is a useful capability to have. I believe @jgarzik also has a use case for this, though I don't know what it is.

As a motivating example I present Lighthouse, an app I'm writing that implements assurance contracts:

Lighthouse works by collecting pledges, which contain an invalid transaction signed with SIGHASH_ANYONECANPAY. Once sufficient pledges are collected to make the combination valid, we say the contract is complete and it can be broadcast onto the network, spending the pledged outputs. Before that occurs however, a pledge can be revoked and the pledged money redeemed by double spending the pledged output. For instance you might want to do this if it becomes clear not enough people care about the assurance...

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