Output Parameters

Output parameters provide a general mechanism to use the result of a step as a parameter (and not just as an artifact). This allows you to use the result from any type of step, not just a script, for conditional tests, loops, and arguments. Output parameters work similarly to script result except that the value of the output parameter is set to the contents of a generated file rather than the contents of stdout.

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: output-parameter-
spec:
  entrypoint: output-parameter
  templates:
  - name: output-parameter
    steps:
    - - name: generate-parameter
        template: whalesay
    - - name: consume-parameter
        template: print-message
        arguments:
          parameters:
          # Pass the hello-param output from the generate-parameter step as the message input to print-message
          - name: message
            value: "{{steps.generate-parameter.outputs.parameters.hello-param}}"

  - name: whalesay
    container:
      image: docker/whalesay:latest
      command: [sh, -c]
      args: ["echo -n hello world > /tmp/hello_world.txt"]  # generate the content of hello_world.txt
    outputs:
      parameters:
      - name: hello-param  # name of output parameter
        valueFrom:
          path: /tmp/hello_world.txt # set the value of hello-param to the contents of this hello-world.txt

  - name: print-message
    inputs:
      parameters:
      - name: message
    container:
      image: docker/whalesay:latest
      command: [cowsay]
      args: ["{{inputs.parameters.message}}"]

DAG templates use the tasks prefix to refer to another task, for example {{tasks.generate-parameter.outputs.parameters.hello-param}}.

result output parameter

The result output parameter captures standard output. It is accessible from the outputs map: outputs.result. Only 256 kb of the standard output stream will be captured.

Scripts

Outputs of a script are assigned to standard output and captured in the result parameter. More details here.

Containers

Container steps and tasks also have their standard output captured in the result parameter. Given a task, called log-int, result would then be accessible as {{ tasks.log-int.outputs.result }}. If using steps, substitute tasks for steps: {{ steps.log-int.outputs.result }}.

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