Native

A Viash component can target one or more platforms. When targeting the native platform, a single executable is generated.

Requirements

The example targets the Native platform, which means you will need to have the required packages installed on your system depending on your chosen scripting language. Take a look at the Scripting Languages page to learn more about a specific language.

Tip

If you want to get started quickly, use Bash as that doesn’t have any external dependencies.

Creating the Viash component

Writing the script

For this example, you’ll use a tiny script that simply outputs “Hello World”, with the “World” part being a variable. To start off, create a folder named hello_world and follow the instructions below based on your preferred scripting language.

Create a new file named script.sh and copy the following content inside of it:

echo "Hello $par_input"

Create a new file named script.csx and copy the following content inside of it:

Console.WriteLine("Hello " + par.input);

Create a new file named script.js and copy the following content inside of it:

console.log('Hello' + par['input']);

Create a new file named script.py and copy the following content inside of it:

print("Hello", par["input"])

Create a new file named script.scala and copy the following content inside of it:

println("Hello " + par.input.get)

Create a new file named script.R and copy the following content inside of it:

cat("Hello ", par$input)

This outputs Hello to the console, followed by an input variable. Notice that this variable isn’t defined in the script itself as Viash will generate it for you based on the config file you’ll create in the next step.

Tip

Every scripting language has its own way of using variables generated by Viash. Check out the Scripting Languages for more information and examples.

Adding the config

A Viash config file is a YAML file that describes the functionality of a component and the platform(s) it targets. Create a file name config.vsh.yaml and add the contents below based on your chosen scripting language.

Download config.vsh.yaml

functionality:
  name: hello_world
  description: A minimal example component.
  arguments:
  - type: string
    name: --input
    default: "World"
  resources:
  - type: bash_script
    path: script.sh
platforms:
  - type: native

Download config.vsh.yaml

functionality:
  name: hello_world
  description: A minimal example component.
  arguments:
  - type: string
    name: --input
    default: "World"
  resources:
  - type: csharp_script
    path: script.csx
platforms:
  - type: native

Download config.vsh.yaml

functionality:
  name: hello_world
  description: A minimal example component.
  arguments:
  - type: string
    name: --input
    default: "World"
  resources:
  - type: javascript_script
    path: script.js
platforms:
  - type: native

Download config.vsh.yaml

functionality:
  name: hello_world
  description: A minimal example component.
  arguments:
  - type: string
    name: --input
    default: "World"
  resources:
  - type: python_script
    path: script.py
platforms:
  - type: native

Download config.vsh.yaml

functionality:
  name: hello_world
  description: A minimal example component.
  arguments:
  - type: string
    name: --input
    default: "World"
  resources:
  - type: scala_script
    path: script.scala
platforms:
  - type: native

Download config.vsh.yaml

functionality:
  name: hello_world
  description: A minimal example component.
  arguments:
  - type: string
    name: --input
    default: "World"
  resources:
  - type: r_script
    path: script.R
platforms:
  - type: native

Here’s a breakdown of the different sections:

functionality describes what the component does and the resources it needs. It contains the name, a short description and more importantly, the arguments and resources the component uses.
- arguments contains all arguments the component accepts and will be passed to the script. In this case, a single string named --input resides here with a default value of World.
- resources holds references to all necessary files and folders to make the component work. For this example, a single script is all that’s needed.
platforms lists what platforms the component can target. This example targets the native platform, which will generate an executable that’s run using the system resources.

Running

With the two necessary files present to create a component, you can call upon Viash to generate a temporary executable and run it:

viash run config.vsh.yaml

Without passing any arguments, this will use the default value for --input, which is World. This results in the following output:

Hello World

By providing the a value for --input, you can customize the greeting:

viash run config.vsh.yaml -- --input Earth

Note

The double dash (--) between the viash command and the arguments is used to signify the end of the arguments passed to viash and the start of those passed to the component. If you forgot to add these, you’ll get an error similar to this:

[scallop] Error: Unknown option 'input'

The example above results in this output:

Hello Earth

What’s next?

To learn how to use Viash to build an executable and run it, see the Native Executable Build Target page.