[[ch03_bitcoin_client]] == The Bitcoin Client === Bitcoin-Qt - The Reference Implementation, aka Satoshi Client You can download the Satoshi Client from bitcoin.org. Depending on your operating system, it will be called bitcoin-qt or bitcoind. The reference client implements all aspects of the bitcoin system, including wallets, a transaction verification engine with a full copy of the entire transaciton ledger (blockchain) and a full network node in the peer-to-peer bitcoin network. Go to http://bitcoin.org/en/choose-your-wallet and select "Bitcoin-Qt" to download the reference client. Depending on your operating system, you will download an executable installer. For Windows, this is either a ZIP archive or an EXE executable. For Mac OS it is DMG disk image. Linux versions include a PPA package for Ubuntu or a TAR.GZ archive. ==== Bitcoin-Qt - Download Options [[bitcoin-qt-dl-options]] .Bitcoin-Qt - Download options for different operating systems image::images/bitcoin-qt-dl-options.png["bitcoin-qt download options"] ==== Bitcoin-Qt - Running the client for the first time If you download an installable package, such as an EXE, DMG or PPA, you can install it the same way as any application on your operating system. For Windows, run the EXE and follow the step-by-step instructions. For Mac OS, launch the DMG and drag the Bitcoin-QT icon into your Applications folder. For Ubuntu, double-click on the PPA in your File Explorer and it will open the package manager to install the package. Once you have completed installation you should have a new application "Bitcoin-Qt" in your application list. Double-click on the icon to start the bitcoin client. The first time you run Bitcoin-Qt it will start downloading the blockchain, a process that may take several days. Leave it running in the background, until it displays "Synchronized" and no longer shows "Out of sync" next to the balance. [TIP] ==== Bitcoin-Qt keeps a full copy of the transaction ledger (blockchain), with every transaction that has ever occured on the bitcoin network since its inception in 2009. This data set is several gigabytes in size (approximately 16GB in late 2013) and is downloaded incrementally over several days. The client will not be able to process transactions or update account balances until the full blockchain dataset is downloaded. During that time, the client will display "Out of sync" next to the account balances and show "Synchronizing" in the footer. Make sure you have enough disk space, bandwidth and time to complete the initial synchronization. ==== [[bitcoin-qt-firstload]] .Bitcoin-Qt - The Graphical User Interface, during the blockchain initialization image::images/bitcoin-qt-firstload.png["bitcoin-qt first run"] ==== Bitcoin-Qt - Compiling the client from the source code For developers, there is also the option to download the full source code, either as a ZIP archive or by cloning the authoritative source repository from Github. Go to https://github.com/bitcoin/bitcoin and select "Download ZIP" from the sidebar. Alternatively, use the git command line to create a local copy of the source code on your system. In the example below, we are cloning the source code from a unix-like command-line, in Linux or Mac OS: ---- $ git clone https://github.com/bitcoin/bitcoin.git Cloning into 'bitcoin'... remote: Counting objects: 31864, done. remote: Compressing objects: 100% (12007/12007), done. remote: Total 31864 (delta 24480), reused 26530 (delta 19621) Receiving objects: 100% (31864/31864), 18.47 MiB | 119 KiB/s, done. Resolving deltas: 100% (24480/24480), done. $ ---- [TIP] ==== The instructions and resulting output may vary from version to version. Follow the documentation that comes with the code even if it differs from the instructions you see here and don't be surprised if the output displayed on your screen is slightly different from the examples here. ==== When the git cloning operation has complete, you will have a complete local copy of the source code repository in the directory _bitcoin_. Change to this directory by typing +cd bitcoin+ at the prompt: ---- $ cd bitcoin ---- By default, the local copy will be synchronized with the most recent code which may be an unstable or "beta" version of bitcoin. Before compiling the code, we want to select a specific version, by checking out a release _tag_. This will synchronize the local copy with a specific snapshot of the code repository identified by a keyword tag. Tags are used by the developers to mark specific releases of the code by version number. First, to find the available tags, we use the +git tag+ command: ---- $ git tag v0.1.5 v0.1.6test1 v0.2.0 v0.2.10 v0.2.11 v0.2.12 [... many more tags ...] v0.8.4rc2 v0.8.5 v0.8.6 v0.8.6rc1 v0.9.0rc1 ---- The list of tags shows all the released versions of bitcoin. By convention, _release candidates_, which are intended for testing, have the suffix "rc". Stable releases that can be run on production systems have no suffix. From the list above, we select the highest version release, which at this time is v0.9.0rc1. To synchronize the local code with this version, we use the +git checkout+ command: ---- $ git checkout v0.9.0rc1 Note: checking out 'v0.9.0rc1'. HEAD is now at 15ec451... Merge pull request #3605 $ ---- The source code includes documentation, which can be found in a number of files. Review the main documentation located in README.md in the bitcoin directory, by typing +more README.md+ at the prompt, using the space bar to progress to the next page. In this chapter we will build the command-line bitcoin client, also known as +bitcoind+ on Linux. Review the instructions for compiling the bitcoind command-line client on your platform by typing +more doc/build-unix.md+. Alternative instructions for Mac OSX and Windows can be found in the doc directory, as +build-os.md+ or +build-msw.md+ respectively. Carefully review the build pre-requisited which are in the first part of the build documentation. These are libraries that must be present on your system before you can begin to compile bitcoin. If these pre-requisites are missing the build process will fail with an error. If this happens because you missed a pre-requisite, you can install it and then resume the build process from where you left off. Assuming the pre-requisites are installed, we start the build process by generating a set of build scripts using the +autogen.sh+ script. [TIP] ==== The bitcoind build process was changed to use the autogen/configure/make system starting with version 0.9. Older versions use a simple Makefile and work slightly differently from the example below. Follow the instructions for the version you want to compile. The autogen/configure/make introduced in 0.9 is likely to be the build system used for all future versions of the code and is the system demonstrated in the examples below. ==== ---- $ ./autogen.sh configure.ac:12: installing `src/build-aux/config.guess' configure.ac:12: installing `src/build-aux/config.sub' configure.ac:37: installing `src/build-aux/install-sh' configure.ac:37: installing `src/build-aux/missing' src/Makefile.am: installing `src/build-aux/depcomp' $ ---- The +autogen.sh+ script creates a set of automatic configuation scripts that will interrogate your system to discover the correct settings and ensure you have all the necessary libraries to compile the code. The most important of these is the +configure+ script that offers a number of different options to customize the build process. Type +./configure --help+ to see the various options: ---- $ ./configure --help `configure' configures Bitcoin Core 0.9.0 to adapt to many kinds of systems. Usage: ./configure [OPTION]... [VAR=VALUE]... To assign environment variables (e.g., CC, CFLAGS...), specify them as VAR=VALUE. See below for descriptions of some of the useful variables. Defaults for the options are specified in brackets. Configuration: -h, --help display this help and exit --help=short display options specific to this package --help=recursive display the short help of all the included packages -V, --version display version information and exit [... many more options and variables are displayed below ...] Optional Features: --disable-option-checking ignore unrecognized --enable/--with options --disable-FEATURE do not include FEATURE (same as --enable-FEATURE=no) --enable-FEATURE[=ARG] include FEATURE [ARG=yes] [... more options ...] Use these variables to override the choices made by `configure' or to help it to find libraries and programs with nonstandard names/locations. Report bugs to . $ ---- The +configure+ script allows you to enable or disable certain features of bitcoind through the use of the +--enable-FEATURE+ and +--disable-FEATURE+ flags, where +FEATURE+ is replaced by the feature name, as listed in the help output above. In this chapter, we will build the bitcoind client with all the default features, so we won't be using these flags, but you should review them to understand what optional features are part of the client. Next, we run the +configure+ script to automatically discover all the necessary libraries and create a customized build script for our system: ---- $ ./configure checking build system type... x86_64-unknown-linux-gnu checking host system type... x86_64-unknown-linux-gnu checking for a BSD-compatible install... /usr/bin/install -c checking whether build environment is sane... yes checking for a thread-safe mkdir -p... /bin/mkdir -p checking for gawk... no checking for mawk... mawk checking whether make sets $(MAKE)... yes [... many more system features are tested ...] configure: creating ./config.status config.status: creating Makefile config.status: creating src/Makefile config.status: creating src/test/Makefile config.status: creating src/qt/Makefile config.status: creating src/qt/test/Makefile config.status: creating share/setup.nsi config.status: creating share/qt/Info.plist config.status: creating qa/pull-tester/run-bitcoind-for-test.sh config.status: creating qa/pull-tester/build-tests.sh config.status: creating src/bitcoin-config.h config.status: executing depfiles commands $ ---- If all goes well, the +configure+ command will end by creating the customized build scripts that will allow us to compile bitcoind. If there are any missing libraries or errors, the +configure+ command will terminate with an error instead of creating the build scripts as shown above. If an error occurs, it is most likely a missing or incompatible library. Review the build documentation again and make sure you install the missing pre-requisites, then run +configure+ again and see if that fixes the error. Next, we will compile the source code, a process that can take up to an hour to complete. During the compilation process you should see output every few seconds or every few minutes, or an error if something goes wrong. The compilation process can be resumed at any time if interrupted. Type +make+ to start compiling: ---- $ make Making all in src make[1]: Entering directory `/home/ubuntu/bitcoin/src' make all-recursive make[2]: Entering directory `/home/ubuntu/bitcoin/src' Making all in . make[3]: Entering directory `/home/ubuntu/bitcoin/src' CXX addrman.o CXX alert.o CXX rpcserver.o CXX bloom.o CXX chainparams.o [... many more compilation messages follow ...] CXX test_bitcoin-wallet_tests.o CXX test_bitcoin-rpc_wallet_tests.o CXXLD test_bitcoin make[4]: Leaving directory `/home/ubuntu/bitcoin/src/test' make[3]: Leaving directory `/home/ubuntu/bitcoin/src/test' make[2]: Leaving directory `/home/ubuntu/bitcoin/src' make[1]: Leaving directory `/home/ubuntu/bitcoin/src' make[1]: Entering directory `/home/ubuntu/bitcoin' make[1]: Nothing to be done for `all-am'. make[1]: Leaving directory `/home/ubuntu/bitcoin' $ ---- If all goes well, bitcoind is now compiled. The final step is to install the bitcoind executable into the system path, using the +make+ command: ---- $ sudo make install Making install in src Making install in . /bin/mkdir -p '/usr/local/bin' /usr/bin/install -c bitcoind bitcoin-cli '/usr/local/bin' Making install in test make install-am /bin/mkdir -p '/usr/local/bin' /usr/bin/install -c test_bitcoin '/usr/local/bin' $ ---- We can confirm that bitcoin is correctly installed, as follows: ---- $ which bitcoind /usr/local/bin/bitcoind ---- The default installation of bitcoind puts it in +/usr/local/bin+. When we first run bitcoind it will remind us to create a configuration file with a strong password for the JSON-RPC interface. We run it by typing +bitcoind+ into the terminal: ---- $ bitcoind Error: To use the "-server" option, you must set a rpcpassword in the configuration file: /home/ubuntu/.bitcoin/bitcoin.conf It is recommended you use the following random password: rpcuser=bitcoinrpc rpcpassword=2XA4DuKNCbtZXsBQRRNDEwEY2nM6M4H9Tx5dFjoAVVbK (you do not need to remember this password) The username and password MUST NOT be the same. If the file does not exist, create it with owner-readable-only file permissions. It is also recommended to set alertnotify so you are notified of problems; for example: alertnotify=echo %s | mail -s "Bitcoin Alert" admin@foo.com ---- Edit the configuration file in your preferred editor and set the parameters, replacing the password with a strong password as recommended by bitcoind. Do *not* use the password shown below. Create a file inside the +.bitcoin+ directory, so that it is named +.bitcoin/bitcoin.conf+ and enter a username and password: ---- rpcuser=bitcoinrpc rpcpassword=7p687uGU8wMyBprB2aQrnt72r9Lh6jZy ---- Now, run the bitcoin client. The first time you run it, it will rebuild the bitcoin blockchain. This is a multi-gigabyte file and will take on average 2 days to download in full. You can shorten the blockchain initialization time by downloading a partial copy of the blockchain using bittorrent from +http://sourceforge.net/projects/bitcoin/files/Bitcoin/blockchain/+. Run bitcoind in the background with the option +-daemon+: ---- $ bitcoind -daemon $ Bitcoin version v0.9.0rc1-beta (2014-01-31 09:30:15 +0100) Using OpenSSL version OpenSSL 1.0.1c 10 May 2012 Default data directory /home/bitcoin/.bitcoin Using data directory /bitcoin/ Using at most 4 connections (1024 file descriptors available) init message: Verifying wallet... dbenv.open LogDir=/bitcoin/database ErrorFile=/bitcoin/db.log Bound to [::]:8333 Bound to 0.0.0.0:8333 init message: Loading block index... Opening LevelDB in /bitcoin/blocks/index Opened LevelDB successfully Opening LevelDB in /bitcoin/chainstate Opened LevelDB successfully [... more startup messages ...] ---- === Using bitcoind from the command line The reference client bitcoind offers a number of commands that can be run from the command line. These are the same commands as those offered via the JSON-RPC API, so the command line allows us to experiment interactively with the capabilities that are also available programmatically. To start, we can invoke the +help+ command to see a list of the available bitcoin commands: [[bitcoind_commands]] .Bitcoind command list ---- addmultisigaddress nrequired ["key",...] ( "account" ) addnode "node" "add|remove|onetry" backupwallet "destination" createmultisig nrequired ["key",...] createrawtransaction [{"txid":"id","vout":n},...] {"address":amount,...} decoderawtransaction "hexstring" decodescript "hex" dumpprivkey "bitcoinaddress" dumpwallet "filename" encryptwallet "passphrase" getaccount "bitcoinaddress" getaccountaddress "account" getaddednodeinfo dns ( "node" ) getaddressesbyaccount "account" getbalance ( "account" minconf ) getbestblockhash getblock "hash" ( verbose ) getblockcount getblockhash index getblocktemplate ( "jsonrequestobject" ) getconnectioncount getdifficulty getgenerate gethashespersec getinfo getmininginfo getnettotals getnetworkhashps ( blocks height ) getnewaddress ( "account" ) getpeerinfo getrawchangeaddress getrawmempool ( verbose ) getrawtransaction "txid" ( verbose ) getreceivedbyaccount "account" ( minconf ) getreceivedbyaddress "bitcoinaddress" ( minconf ) gettransaction "txid" gettxout "txid" n ( includemempool ) gettxoutsetinfo getunconfirmedbalance getwork ( "data" ) help ( "command" ) importprivkey "bitcoinprivkey" ( "label" rescan ) importwallet "filename" keypoolrefill ( newsize ) listaccounts ( minconf ) listaddressgroupings listlockunspent listreceivedbyaccount ( minconf includeempty ) listreceivedbyaddress ( minconf includeempty ) listsinceblock ( "blockhash" target-confirmations ) listtransactions ( "account" count from ) listunspent ( minconf maxconf ["address",...] ) lockunspent unlock [{"txid":"txid","vout":n},...] move "fromaccount" "toaccount" amount ( minconf "comment" ) ping sendfrom "fromaccount" "tobitcoinaddress" amount ( minconf "comment" "comment-to" ) sendmany "fromaccount" {"address":amount,...} ( minconf "comment" ) sendrawtransaction "hexstring" ( allowhighfees ) sendtoaddress "bitcoinaddress" amount ( "comment" "comment-to" ) setaccount "bitcoinaddress" "account" setgenerate generate ( genproclimit ) settxfee amount signmessage "bitcoinaddress" "message" signrawtransaction "hexstring" ( [{"txid":"id","vout":n,"scriptPubKey":"hex","redeemScript":"hex"},...] ["privatekey1",...] sighashtype ) stop submitblock "hexdata" ( "jsonparametersobject" ) validateaddress "bitcoinaddress" verifychain ( checklevel numblocks ) verifymessage "bitcoinaddress" "signature" "message" ---- ==== Command: bitcoind getinfo Bitcoin's +getinfo+ command shows us basic information about the status of the bitcoin network node, the wallet and the blockchain database: ---- $ bitcoind getinfo { "version" : 90000, "protocolversion" : 70002, "walletversion" : 60000, "balance" : 0.00000000, "blocks" : 286216, "timeoffset" : -72, "connections" : 4, "proxy" : "", "difficulty" : 2621404453.06461525, "testnet" : false, "keypoololdest" : 1374553827, "keypoolsize" : 101, "paytxfee" : 0.00000000, "errors" : "" } ---- The data is returned as a JavaScript Object Notation (JSON), a format which can easily be "consumed" by all programming languages but is also quite human-readable. Among this data we see the version of the bitcoin software client (9000), protocol (70002) and wallet file (60000). We see the current balance contained in the wallet, which is zero. We see the current block height, showing us how many blocks are known to this client, 286216. We also see various statistics about the bitcoin network and the settings related to this client. We will explore these settings in more detail in the rest of this chapter. [TIP] ==== It will take some time, perhaps more than a day, for the bitcoind client to "catch up" to the current blockchain height as it downloads blocks from other bitcoin clients. You can check its current progress using getinfo to see the number of known blocks. ==== ==== Commands: bitcoind encryptwallet, walletpassphrase Before we proceed with creating keys and other commands, we will first encrypt the wallet with a password. For this example, we use the +encryptwallet+ command with the password "foo". Obviously, replace "foo" with a strong and complex password! ---- $ bitcoind encryptwallet foo wallet encrypted; Bitcoin server stopping, restart to run with encrypted wallet. The keypool has been flushed, you need to make a new backup. $ ---- We can verify the wallet has been encrypted, by running +getinfo+ again. This time you will notice a new entry +unlocked_until+ which is a counter showing how long the wallet decryption password will be stored in memory, keeping the wallet unlocked. At first this will be set to zero, meaning the wallet is locked: ---- $ bitcoind getinfo { "version" : 90000, [... other information...] "unlocked_until" : 0, "errors" : "" } $ ---- To unlock the wallet, we issue the +walletpassphrase+ command that takes two parameters, the password and a number of seconds until the wallet is locked again automatically (a time counter): ---- $ bitcoind walletpassphrase foo 360 $ ---- Confirm the wallet is unlocked and see the timeout by running +getinfo+ again: ---- $ bitcoind getinfo { "version" : 90000, [... other information ...] "unlocked_until" : 1392580909, "errors" : "" } ---- ==== Commands: backupwallet, importwallet, dumpwallet Next, we will practice creating a wallet backup file and then restoring the wallet from the backup file. Use the +backupwallet+ command to backup, providing the file name as the parameter. Here we backup the wallet to the file +wallet.backup+: ---- $ bitcoind backupwallet wallet.backup $ ---- Now, to restore the backup file, use the +importwallet+ command. If your wallet is locked, you will need to unlock it first (see +walletpassphrase+ above) in order to import the backup file: ---- $ bitcoind importwallet wallet.backup $ ---- The +dumpwallet+ command can be used to dump the wallet into a text file that is human-readable: ---- $ bitcoind dumpwallet wallet.txt $ more wallet.txt # Wallet dump created by Bitcoin v0.9.0rc1-beta (2014-01-31 09:30:15 +0100) # * Created on 2014-02- 8dT20:34:55Z # * Best block at time of backup was 286234 (0000000000000000f74f0bc9d3c186267bc45c7b91c49a0386538ac24c0d3a44), # mined on 2014-02- 8dT20:24:01Z KzTg2wn6Z8s7ai5NA9MVX4vstHRsqP26QKJCzLg4JvFrp6mMaGB9 2013-07- 4dT04:30:27Z change=1 # addr=16pJ6XkwSQv5ma5FSXMRPaXEYrENCEg47F Kz3dVz7R6mUpXzdZy4gJEVZxXJwA15f198eVui4CUivXotzLBDKY 2013-07- 4dT04:30:27Z change=1 # addr=17oJds8kaN8LP8kuAkWTco6ZM7BGXFC3gk [... many more keys ...] $ ---- ==== Commands: getnewaddress, getreceivedbyaddress, listtransactions, getaddressesbyaccount, getbalance The bitcoin reference client maintains a pool of addresses, the size of which is displayed by +keypoolsize+ when you use the command +getinfo+. These addresses are generated automatically and can then be used as public receiving addresses or change addresses. To get one of these addresses, you can use the +getnewaddress+ command: ---- $ bitcoind getnewaddress 1hvzSofGwT8cjb8JU7nBsCSfEVQX5u9CL ---- Now, we can use this address to send a small amount of bitcoin to our bitcoind wallet from an external wallet (assuming you have some bitcoin in an exchange, web wallet or othe bitcoind wallet held elsewhere). For this example, we will send 50 millibits (0.050 bitcoin) to the address returned above. We can now query the bitcoind client for the amount received by this address, and specify how many confirmations are required before an amount is counted in that balance. For this example, we will specify zero confirmations. A few seconds after sending the bitcoin from another wallet, we will see it reflected in the wallet. We use +getreceivedbyaddress+ with the address and the number of confirmations set to zero (0): ---- $ bitcoind getreceivedbyaddress 1hvzSofGwT8cjb8JU7nBsCSfEVQX5u9CL 0 0.05000000 ---- If we ommit the zero from the end of this command, we will only see the amounts that have at least +minconf+ confirmations, where +minconf+ is the setting for the minimum number of confirmations before a transaction is ilsted in the balance. The +minconf+ setting is specified in the bitcoind configuration file. Since the transaction sending this bitcoin was only sent in the last few seconds, it has still not confirmed and therefore we will see it list a zero balance: ---- $ bitcoind getreceivedbyaddress 1hvzSofGwT8cjb8JU7nBsCSfEVQX5u9CL 0.00000000 ---- The transactions received by the entire wallet can also be displayed using the +listtransactions+ command: ---- $ bitcoind listtransactions [ { "account" : "", "address" : "1hvzSofGwT8cjb8JU7nBsCSfEVQX5u9CL", "category" : "receive", "amount" : 0.05000000, "confirmations" : 0, "txid" : "9ca8f969bd3ef5ec2a8685660fdbf7a8bd365524c2e1fc66c309acbae2c14ae3", "time" : 1392660908, "timereceived" : 1392660908 } ] ---- We can list all addresses in the entire wallet using the +getaddressesbyaccount+ command: ---- $ bitcoind getaddressesbyaccount "" [ "1LQoTPYy1TyERbNV4zZbhEmgyfAipC6eqL", "17vrg8uwMQUibkvS2ECRX4zpcVJ78iFaZS", "1FvRHWhHBBZA8cGRRsGiAeqEzUmjJkJQWR", "1NVJK3JsL41BF1KyxrUyJW5XHjunjfp2jz", "14MZqqzCxjc99M5ipsQSRfieT7qPZcM7Df", "1BhrGvtKFjTAhGdPGbrEwP3xvFjkJBuFCa", "15nem8CX91XtQE8B1Hdv97jE8X44H3DQMT", "1Q3q6taTsUiv3mMemEuQQJ9sGLEGaSjo81", "1HoSiTg8sb16oE6SrmazQEwcGEv8obv9ns", "13fE8BGhBvnoy68yZKuWJ2hheYKovSDjqM", "1hvzSofGwT8cjb8JU7nBsCSfEVQX5u9CL", "1KHUmVfCJteJ21LmRXHSpPoe23rXKifAb2", "1LqJZz1D9yHxG4cLkdujnqG5jNNGmPeAMD" ] ---- Finally, the command +getbalance+ will show the total balance of the wallet, adding up all transactions confirmed with at least +minconf+ confirmations: ---- $ bitcoind getbalance 0.05000000 ---- [TIP] ==== If the transaction has not yet confirmed, the balance returned by getbalance will be zero. The configuration option "minconf" determines the minimum number of confirmations that are required before a transaction shows in the balance ==== ==== Commands: gettransaction, getrawtransaction, decoderawtransaction We'll now explore the incoming transaction that was listed above, using the +gettransaction+. We can retrieve a transaction by its transaction hash, shown at +txid+, above with the +gettransaction+ command: ---- $ bitcoind gettransaction 9ca8f969bd3ef5ec2a8685660fdbf7a8bd365524c2e1fc66c309acbae2c14ae3 { "amount" : 0.05000000, "confirmations" : 0, "txid" : "9ca8f969bd3ef5ec2a8685660fdbf7a8bd365524c2e1fc66c309acbae2c14ae3", "time" : 1392660908, "timereceived" : 1392660908, "details" : [ { "account" : "", "address" : "1hvzSofGwT8cjb8JU7nBsCSfEVQX5u9CL", "category" : "receive", "amount" : 0.05000000 } ] } ---- [TIP] ==== Transaction IDs are not authoritative until a transaction has been confirmed. Absence of a transaction hash in the blockchain does not mean the transaction was not processed. This is known as "transaction malleability", as transaction hashes can be modified prior to confirmation in a block. After confirmation, the txid is immutable and authoritative. ==== The transaction form shown above with the command +gettransaction+ is the simplified form. To retrieve the full transaction code and decode it we will use two commands, +getrawtransaction+ and +decoderawtransaction+. First, +getrawtransaction+ takes the transaction hash (txid) as a parameter and returns the full transaction as a "raw" hex string, exactly as it exists on the bitcoin network: ---- $ bitcoind getrawtransaction 9ca8f969bd3ef5ec2a8685660fdbf7a8bd365524c2e1fc66c309acbae2c14ae3 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 ---- To decode this hex string, we can use the +decoderawtransaction+ command. Copy and paste the hex as the first parameter of +decoderawtransaction+ to get the full contents interpreted as a JSON data structure (for formatting reasons the hex string is shortened in the example below): ---- $ bitcoind decoderawtransaction 0100000001d717...388ac00000000 { "txid" : "9ca8f969bd3ef5ec2a8685660fdbf7a8bd365524c2e1fc66c309acbae2c14ae3", "version" : 1, "locktime" : 0, "vin" : [ { "txid" : "d3c7e022ea80c4808e64dd0a1dba009f3eaee2318a4ece562f8ef815952717d7", "vout" : 0, "scriptSig" : { "asm" : "3045022100a4ebbeec83225dedead659bbde7da3d026c8b8e12e61a2df0dd0758e227383b302203301768ef878007e9ef7c304f70ffaf1f2c975b192d34c5b9b2ac1bd193dfba201 04793ac8a58ea751f9710e39aad2e296cc14daa44fa59248be58ede65e4c4b884ac5b5b6dede05ba84727e34c8fd3ee1d6929d7a44b6e111d41cc79e05dbfe5cea", "hex" : "483045022100a4ebbeec83225dedead659bbde7da3d026c8b8e12e61a2df0dd0758e227383b302203301768ef878007e9ef7c304f70ffaf1f2c975b192d34c5b9b2ac1bd193dfba2014104793ac8a58ea751f9710e39aad2e296cc14daa44fa59248be58ede65e4c4b884ac5b5b6dede05ba84727e34c8fd3ee1d6929d7a44b6e111d41cc79e05dbfe5cea" }, "sequence" : 4294967295 } ], "vout" : [ { "value" : 0.05000000, "n" : 0, "scriptPubKey" : { "asm" : "OP_DUP OP_HASH160 07bdb518fa2e6089fd810235cf1100c9c13d1fd2 OP_EQUALVERIFY OP_CHECKSIG", "hex" : "76a91407bdb518fa2e6089fd810235cf1100c9c13d1fd288ac", "reqSigs" : 1, "type" : "pubkeyhash", "addresses" : [ "1hvzSofGwT8cjb8JU7nBsCSfEVQX5u9CL" ] } }, { "value" : 1.03362847, "n" : 1, "scriptPubKey" : { "asm" : "OP_DUP OP_HASH160 107b7086b31518935c8d28703d66d09b36231343 OP_EQUALVERIFY OP_CHECKSIG", "hex" : "76a914107b7086b31518935c8d28703d66d09b3623134388ac", "reqSigs" : 1, "type" : "pubkeyhash", "addresses" : [ "12W9goQ3P7Waw5JH8fRVs1e2rVAKoGnvoy" ] } } ] } ---- The transaction decode shows all the compoenents of this transaction, including the transaction inputs, and outputs. In this case we see that the transaction that credited our new address with 50 milibits used one input and generated two outputs. The input to this transaction was the output from a previously confirmed transaction (shown as the vin txid starting with +d3c7+ above). The two outputs correspond to the 50 milibit credit and an output with change back to the sender. We can further explore the blockchain by examining the previous transaction referenced by its txid in this transaction, using the same commands (eg. +gettransaction+). Jumping from transaction to transaction we can follow a chain of transactions back as the coins are transmitted from owner address to owner address. Once the transaction we received has been confirmed, by inclusion in a block, the +gettransaction+ command will return additional information, showing the block hash (identifier) in which the transaction was included: ---- $ bitcoind gettransaction 9ca8f969bd3ef5ec2a8685660fdbf7a8bd365524c2e1fc66c309acbae2c14ae3 { "amount" : 0.05000000, "confirmations" : 1, "blockhash" : "000000000000000051d2e759c63a26e247f185ecb7926ed7a6624bc31c2a717b", "blockindex" : 18, "blocktime" : 1392660808, "txid" : "9ca8f969bd3ef5ec2a8685660fdbf7a8bd365524c2e1fc66c309acbae2c14ae3", "time" : 1392660908, "timereceived" : 1392660908, "details" : [ { "account" : "", "address" : "1hvzSofGwT8cjb8JU7nBsCSfEVQX5u9CL", "category" : "receive", "amount" : 0.05000000 } ] } ---- Above, we see the new information in the entries +blockhash+, the hash of the block in which the transaction was included, and +blockindex+ with value 18, indicating that our transaction was the 18th transaction in that block. ==== Commands: getblock Now that we know which block our transaction was included in, we can query that block. We use the +getblock+ command with the block hash as the parameter: ---- $ bitcoind getblock 000000000000000051d2e759c63a26e247f185ecb7926ed7a6624bc31c2a717b true { "hash" : "000000000000000051d2e759c63a26e247f185ecb7926ed7a6624bc31c2a717b", "confirmations" : 2, "size" : 248758, "height" : 286384, "version" : 2, "merkleroot" : "9891747e37903016c3b77c7a0ef10acf467c530de52d84735bd55538719f9916", "tx" : [ "46e130ab3c67d31d2b2c7f8fbc1ca71604a72e6bc504c8a35f777286c6d89bf0", "2d5625725b66d6c1da88b80b41e8c07dc5179ae2553361c96b14bcf1ce2c3868", "923392fc41904894f32d7c127059bed27dbb3cfd550d87b9a2dc03824f249c80", "f983739510a0f75837a82bfd9c96cd72090b15fa3928efb9cce95f6884203214", "190e1b010d5a53161aa0733b953eb29ef1074070658aaa656f933ded1a177952", "ee791ec8161440262f6e9144d5702f0057cef7e5767bc043879b7c2ff3ff5277", "4c45449ff56582664abfadeb1907756d9bc90601d32387d9cfd4f1ef813b46be", "3b031ed886c6d5220b3e3a28e3261727f3b4f0b29de5f93bc2de3e97938a8a53", "14b533283751e34a8065952fd1cd2c954e3d37aaa69d4b183ac6483481e5497d", "57b28365adaff61aaf60462e917a7cc9931904258127685c18f136eeaebd5d35", "8c0cc19fff6b66980f90af39bee20294bc745baf32cd83199aa83a1f0cd6ca51", "1b408640d54a1409d66ddaf3915a9dc2e8a6227439e8d91d2f74e704ba1cdae2", "0568f4fad1fdeff4dc70b106b0f0ec7827642c05fe5d2295b9deba4f5c5f5168", "9194bfe5756c7ec04743341a3605da285752685b9c7eebb594c6ed9ec9145f86", "765038fc1d444c5d5db9163ba1cc74bba2b4f87dd87985342813bd24021b6faf", "bff1caa9c20fa4eef33877765ee0a7d599fd1962417871ca63a2486476637136", "d76aa89083f56fcce4d5bf7fcf20c0406abdac0375a2d3c62007f64aa80bed74", "e57a4c70f91c8d9ba0ff0a55987ea578affb92daaa59c76820125f31a9584dfc", "9ca8f969bd3ef5ec2a8685660fdbf7a8bd365524c2e1fc66c309acbae2c14ae3", [... many more transactions ...] ], "time" : 1392660808, "nonce" : 3888130470, "bits" : "19015f53", "difficulty" : 3129573174.52228737, "chainwork" : "000000000000000000000000000000000000000000001931d1658fc04879e466", "previousblockhash" : "0000000000000000177e61d5f6ba6b9450e0dade9f39c257b4d48b4941ac77e7", "nextblockhash" : "0000000000000001239d2c3bf7f4c68a4ca673e434702a57da8fe0d829a92eb6" } ---- The block contains 367 transactions and as you see above, the 18th transaction listed (+9ca8f9...+) is the txid of the one crediting 50 millibits to our address. The +height+ entry tells us this is the 286384'th block in the blockchain. We can also retrieve a block by its block height, using the +getblockhash+ command, which takes the block height as the parameter and returns the block hash for that block: ---- $ bitcoind getblockhash 0 000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f ---- Above, we retrieve the block hash of the "genesis block", the first block mined by Satoshi Nakamoto, at height zero. Retrieving this block shows: ---- $ bitcoind getblock 000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f { "hash" : "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f", "confirmations" : 286388, "size" : 285, "height" : 0, "version" : 1, "merkleroot" : "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b", "tx" : [ "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b" ], "time" : 1231006505, "nonce" : 2083236893, "bits" : "1d00ffff", "difficulty" : 1.00000000, "chainwork" : "0000000000000000000000000000000000000000000000000000000100010001", "nextblockhash" : "00000000839a8e6886ab5951d76f411475428afc90947ee320161bbf18eb6048" } ---- The +getblock+, +getblockhash+ and +gettransaction+ commands can be used to explore the blockchain database, programmatically.