pre-requisite

This part assumes you've created at least one account.
If not, please check the previous post EOS Dev Guide 0x02.

Compile contract

contract needs to be first compiled to .wasm format as a bin file.
Then generate the .abi file to serve as a function interface index file.

create .cpp file

First, cd to any place and make a new folder to place the contract code.

$ mkdir -p ~/eos-dev/helloworld
$ cd ~/eos-dev/helloworld
$ vim helloworld.cpp

Then place the following code, save and quite(:wq)

#include <eosiolib/eosio.hpp>
#include <eosiolib/print.hpp>

using namespace eosio;

class helloworld : public eosio::contract {
  public:
      using contract::contract;

      void hello(account_name user) {
         print("Hello world! ", name{user});
      }
};

EOSIO_ABI(helloworld, (hello))

compile to .wasm and .wast

$ eosiocpp -o helloworld.wast helloworld.cpp

This will generate .wast and .wasm at the same time.
.wast file is the text version of .wasm

NOTE: if you encountered exceptions saying something like couldn't find file 'eosiolib/eosio.hpp', then try sudo eosiocpp -o ....

generate .abi file

$ eosiocpp -g helloworld.abi helloworld.cpp

alright, we've finished the preparation work.

Publish contract

In EOS, a contract needs to be attached to an account, functions would become actions of that account.

For our test purpose, we are going to publish the helloworld contract on test.hello account and use it.

First, cd to helloworld/../, which is the upper dir of our contract folder, in this example, it would be /eos-dev

$ cd /path/to/upper/dir/of/contract/folder
$ cleos set contract test.hello helloworld
Reading WAST/WASM from helloworld/helloworld.wasm...
Using already assembled WASM...
Publishing contract...
executed transaction: 6976f392d97728841a28ce7fb0e39734dd4ae58f9da5872cf9eeb3d2ddedd1f7  1808 bytes  569 us
#         eosio <= eosio::setcode               {"account":"test.hello","vmtype":0,"vmversion":0,"code":"0061736d01000000013b0c60027f7e006000017e600...
#         eosio <= eosio::setabi                {"account":"test.hello","abi":"0e656f73696f3a3a6162692f312e3000010568656c6c6f00010475736572046e616d6...
warning: transaction executed locally, but may not be confirmed by the network yet

Call contract function

$ cleos push action test.hello hello '["test.hello"]' -p test.hello
executed transaction: a0d226570d79330ea1e837e4c9da30080e92224cca83fbe564307bb7e873ac26  104 bytes  491 us
#    test.hello <= test.hello::hello            {"user":"test.hello"}
>> Hello world! test.hello
warning: transaction executed locally, but may not be confirmed by the network yet

NOTE: if you didn't get any output, check if you used --contracts-console flag when starting nodeos. (ref)

And you'll see the same output in the nodeos output.

$ cleos push action test.hello hello '["test.hello"]' -p test.hello
executed transaction: a0d226570d79330ea1e837e4c9da30080e92224cca83fbe564307bb7e873ac26  104 bytes  491 us
#    test.hello <= test.hello::hello            {"user":"test.hello"}
>> Hello world! test.hello
warning: transaction executed locally, but may not be confirmed by the network yet

End

Congrats! We've deployed and executed an EOS contract!
There are more contract examples under eos/build/contracts, the source code is under eos/contracts.

Alright, so much for this post, hope you enjoy.

Peace.