How to customize my own commands in geth console?

We know that in geth console, we can type eth.accounts and other commands. I found that there is a JavaScript parser/interpreter named Otto which does this, But how to add a new command such as eth.mycommand in geth console?

Thank you very much.

2 Answers 2


You can modify source code to achieve, creating a local private chain.

  1. Install go

  2. Clone go-ethereum project by git clone https://github.com/ethereum/go-ethereum.git

  3. Rebuild all commands by make all, for instance geth
  4. Test whether everything is ok. ./build/bin/geth --datadir=./dev/data0 --networkid 2 console. At first you should create directory ./dev/data0 to save chain data. If Ok, now you have entered geth console.

Now, we modify the source code. when geth starting, a thread will be created to interact with console by Interactive method, and last console.Evaluate() will deal with input command. So you can implement your logic in here. Now we define a eth.custom(params) command to show say-hello. Modify source code as follows:

// Evaluate executes code and pretty prints the result to the specified output
// stream.
func (c *Console) Evaluate(statement string) error {
    if (isCustomCommand(statement)) {//custom command,return
        result := "Hello " + statement[strings.Index(statement,"\"")+1:len(statement)-3]
        return nil
    defer func() {
        if r := recover(); r != nil {
            fmt.Fprintf(c.printer, "[native] error: %v\n", r)
    return c.jsre.Evaluate(statement, c.printer)

//our custom is eth.custom(param)
func isCustomCommand(input string) bool{
    return strings.HasPrefix(input,"eth.custom")

If you input eth.custom("BinBin"), it shows Hello BinBin on terminal. Now execute

make all

command to rebuild, and then execute command to enter console:

./build/bin/geth --datadir=./dev/data0 --networkid 2  console

Now, we start test, input command as follows:


and the result is

enter image description here

Hope it helps~


Geth does provide the parameters --jspath, --preload and --exec that can be used to customize the console.

Also there is https://github.com/ethereum/ethereum-console which you can use to create your own console.

  • thank you , I just want to customize new command such as admin.sayHello,how to modify the source to achieve the goal?
    – jiebang
    Commented Jun 23, 2017 at 13:17
  • 1
    From the console you can do admin.sayHello = function (who) { console.log('Hello ' + who); }. Now you can do from the console admin.sayHello('World!') and it will hecho "Hello World!".
    – Ismael
    Commented Jun 23, 2017 at 16:47
  • Maybe it is useful, but I want to create some complicated command which can't be achieved by assembling existing commands.
    – jiebang
    Commented Jun 27, 2017 at 5:41

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.