Ethereum first smart contract

Launch your geth (or testrpc) private instance

./geth \
    --identity "gethTest" \
    --rpc --rpcport "9012" \
    --rpccorsdomain "YOUR_TEST_DOMAIN_APP_RUN_FROM" \
    --datadir "./testChain" \
    --port "30303" \
    --nodiscover \
    --rpcapi "db,eth,net,web3" \
    --networkid 1999 \
    --dev console

Within the console, compile your contract

check this tutorial: https://www.ethereum.org/greeter

I had an issue when I followed the contract tutorial, my contract would not be mined after I was trying to deploy it.

The issue was that my account was locked :/ and the greeter contract stupidly silently fails… Here is the modified code to see the obvious error.

var _greeting = "Hello World!"
var greeterContract = web3.eth.contract(greeterCompiled.greeter.info.abiDefinition);

var greeter = greeterContract.new(_greeting,{from:web3.eth.accounts[0], data: greeterCompiled.greeter.code, gas: 30000000}, function(e, contract){
    if(!e) {

      if(!contract.address) {
        console.log("Contract transaction send: TransactionHash: " + contract.transactionHash + " waiting to be mined...");

      } else {
        console.log("Contract mined! Address: " + contract.address);
        console.log(contract);
      }

    } else {
        console.log("error!");
        console.log(e);
    }
})

which returns

error!
Error: account is locked

To unlock the account, simply:

personal.unlockAccount(eth.accounts[0])

I then encountered ANOTHER error!

error!
Error: Exceeds block gas limit

I simply decreased the gas to 3000000, and finally got:

I0803 15:14:29.423492 eth/api.go:1191] Tx(0x7584a963a9c2a21e623e607826ad47ae358d056ed159b82a21793d4541148e86) created: 0x5f3425ccedeae0eb36521c4cf93ec6544dbad9bd
Contract transaction send: TransactionHash: 0x7284a963a9c3a21e623e607826ad47ae358d056ed159b82a21793d4541148e86 waiting to be mined...

Then, simply mine it!

miner.start()
...
Contract mined! Address: 0x5d3125ccedeae0eb36521c4cf93ec6544dbad9bd
...
miner.stop()

Yeah, victory! my contract is deployed on my private ethereum node.

Keep that address and also make sure to run

greeterCompiled.greeter.info.abiDefinition

in order to get the ABI that will be used later in javascript (Application Binary Interface)

[{
    constant: false,
    inputs: [],
    name: "kill",
    outputs: [],
    type: "function"
}, {
    constant: true,
    inputs: [],
    name: "greet",
    outputs: [{
        name: "",
        type: "string"
    }],
    type: "function"
}, {
    inputs: [{
        name: "_greeting",
        type: "string"
    }],
    type: "constructor"
}]

When done, kill it!

greeter.kill.sendTransaction({from:eth.accounts[0]})

Next we will simply interact with the contract.