Hello, workflow!

Overview

This section introduces you the concepts of row projects, workspaces, and actions. It also demonstrates how to submit actions.

Initializing a project

All row commands operate on the current project directory which contains the file workflow.toml and a workspace directory. Create a new directory hello-workflow and initialize a project there:

row init hello-workflow
cd hello-workflow

Row helps you organize your workflow into distinct actions that each execute on one (or more) directories in the workspace. row init created an empty workspace. You must add directories so that your actions have something to work on:

mkdir workspace/directory0 workspace/directory1 workspace/directory2

These directories may have any name. Row will identify any directory at the top level of workspace as a potential target for each action.

Defining a workflow

Now that you have a workspace, you can define an action to execute. Replace the empty workflow.toml file that row init created with:

[[action]]
name = "hello"
command = 'echo "Hello, {directory}!"'

workflow.toml is a TOML file. In workflow.toml, action is an array of tables and each [[action]] line adds a new element. Each element requires the keys name and command. There are many optional keys you will learn about in later tutorials, or you can skip ahead and read the action reference documentation.

name is a string that sets the name of the action. command is a template for a shell command that row will execute on each directory. The {directory} in command will be replaced with directory names.

Submitting jobs

Execute:

row submit

to submit jobs that execute the actions in the workflow.

You should see:

Submitting 1 job that may cost up to 3 CPU-hours.
Proceed? [Y/n]:

The cost is 3 CPU-hours because action defaults to 1 CPU-hour per directory (later sections in this tutorial will cover resource costs in more detail). echo "Hello, {directory}!" is certainly not going to take that long, so confirm with y and then press enter. You should then see the action execute:

[1/1] Submitting action 'hello' on directory directory0 and 2 more.
Hello, directory0!
Hello, directory1!
Hello, directory2!

As an exercise, read the row submit documentation and see if you can find a way to submit this workflow only on directory2.

Next steps

You have created your first row workflow and executed it! The next section of this tutorial will show you how to configure one action that will execute after another action completes.

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