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Hello World

The following is a simple example to give you an idea of how CloudSlang is structured and can be used to ensure your environment is set up properly.

Prerequisites

This example uses the CloudSlang CLI to run a flow. See the :doc:`CloudSlang CLI <cloudslang_cli>` section for instructions on how to download and run the CLI.

Although CloudSlang files can be composed in any text editor, using a modern code editor with support for YAML syntax highlighting is recommended. See :doc:`CloudSlang Editors <cloudslang_editors>` for instructions on how to download, install and use the CloudSlang language package for Atom.

Code files

:download:`Download </code/examples_code/examples/hello_world.zip>` the code or use the following instructions:

Create a folder examples and then another folder hello_world inside the examples folder. In the hello_world folder, create two new CloudSlang files, hello_world.sl and print.sl.

You should now have the following folder structure:

  • examples

    • hello_world

      • hello_world.sl
      • print.sl

Copy the code below into the corresponding files.

hello_world.sl

namespace: examples.hello_world

flow:
  name: hello_world

  workflow:
    - sayHi:
        do:
          print:
            - text: "Hello, World"

print.sl

namespace: examples.hello_world

operation:
  name: print

  inputs:
    - text

  python_action:
    script: print text

  results:
    - SUCCESS

Run

Start the CLI and enter the following command at the cslang> prompt:

run --f <path_to_files>/examples/hello_world/hello_world.sl --cp <path_to_files>/examples/hello_world

Note

Use forward slashes in the file paths.

The output will look similar to this:

- sayHi
Hello, World
Flow : hello_world finished with result : SUCCESS
Execution id: 101600001, duration: 0:00:00.790

Explanation

The CLI runs the :ref:`flow` contained in the file passed to it using the --f flag, namely hello_world.sl. The --cp flag is used to specify the classpath where the flow's dependencies can be found. In our case, the flow refers to the print operation, so we must add its location to the classpath.

Note

If you are using a CLI without the content folder, specifying the classpath in this instance is not necessary.

The :ref:`flow` named hello_world begins its :ref:`workflow`. The :ref:`workflow` has one :ref:`step` named sayHi which calls the print :ref:`operation`. The :ref:`flow` passes the string "Hello, World" to the text :ref:`input <inputs>` of the print :ref:`operation`. The print :ref:`operation` performs its :ref:`python_action`, which is a simple Python script that prints the :ref:`input <inputs>`, and then returns a :ref:`result <results>` of SUCCESS. Since the flow does not contain any more :ref:`steps <step>` the :ref:`flow` finishes with a :ref:`result <results>` of SUCCESS.

More

For a more comprehensive walkthrough of the CloudSlang language's features, see the :doc:`tutorial <tutorial/01_lesson>`.