Do they have a client installed on their servers that pulls the info out of block headers? How does it do it? What's the command?
Blockchain.info definitely has a client installed on their servers, that's where they get all the block data from. I heard they're using a fork of BitcoinJ.
In the Bitcoin-qt daemon, you can get the difficulty of the latest block with the getdifficulty command, and you can get complete information about every block, including the difficulty, with getblock.
How would I do it without a UI, say, if I installed bitcoind on my server? Dec 7, 2012 at 7:08
If you can access it with a CLI, you can go to the daemon directory and run bitcoind.exe with the required command as a parameter. Other than that there's something called JSON-RPC but I don't really know what that is. Dec 7, 2012 at 7:54
Drats, I have a Mac . . . Dec 14, 2012 at 2:44
@KinnardHockenhull: Are you talking about a computer you have locally? I don't know how Macs work, but doesn't it have a command prompt? Dec 14, 2012 at 4:37
@KinnardHockenhull Open up spotlight and type in "terminal" for the command line. If your bitcoind instance has JSON-RPC enabled through config you can use CURL to access the data Mar 3, 2013 at 23:22