Developer Guide

First CLI Module

Create a directory cli-say-hello

mkdir cli-say-hello
cd cli-say-hello

Initialize a new project in cli-say-hello:

go mod init cli-say-hello

Install the Capsule MDK dependencies:

go get github.com/bots-garden/capsule-module-sdk

Create a new file main.go in cli-say-hello:

package main

import (
    capsule "github.com/bots-garden/capsule-module-sdk"
)

func main() {
    capsule.SetHandle(Handle)
}

// Handle function
func Handle(params []byte) ([]byte, error) {

    // Display the content of `params`
    capsule.Print("Module parameter(s): " + string(params))

    // Read an display an environment variable 
    capsule.Print("MESSAGE: " + capsule.GetEnv("MESSAGE"))

    // Write content to a file
    err := capsule.WriteFile("./hello.txt", []byte("👋 Hello World! 🌍"))
    if err != nil {
        capsule.Print(err.Error())
    }

    // Read content from a file
    data, err := capsule.ReadFile("./hello.txt")
    if err != nil {
        capsule.Print(err.Error())
    }
    capsule.Print("📝: " + string(data))

    return []byte("👋 Hello " + string(params)), nil

}

• capsule.SetHandle(Handle) defines the called wasm function
• capsule.Print(), capsule.GetEnv(), capsule.WriteFile() and capsule.ReadFile() are host functions defined in the Capsule HDK https://github.com/bots-garden/capsule-host-sdk

Build the wasm module:

tinygo build -o cli-say-hello.wasm -scheduler=none --no-debug -target wasi ./main.go

Run the module:

You need to download the last capsule CLI: https://github.com/bots-garden/capsule/releases

export MESSAGE="👋 Hello Capsule"
./capsule --wasm=cli-say-hello.wasm --params="Jane Doe"

- --wasm flag: the path to the wasm file - --mode flag: the parameter to pass to the wasm module

output:

Module parameter(s): Jane Doe
MESSAGE: 👋 Hello Capsule
📝: 👋 Hello World! 🌍
👋 Hello Jane Doe

You can find more samples on /capsule/capsule-cli