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Orchestrating Shell Commands with Prefect

Harness the power of the Prefect CLI to execute and schedule shell commands as Prefect flows. This guide focuses on using the watch and serve commands to showcase the CLI's versatility for automation tasks.

Here's what you'll learn:

  • Running a shell command as a Prefect flow on-demand with watch.
  • Scheduling a shell command as a recurring Prefect flow using serve.
  • The benefits of embedding these commands into your automation workflows.

Prerequisites

Before you begin, ensure you have:

  • An introductory understanding of Prefect and flow concepts. Start with the Getting Started guide if you're new.
  • Prefect CLI installed, following the instructions in the Prefect documentation.
  • A command-line environment ready for executing commands.

The watch Command

The watch command wraps any shell command in a Prefect flow for instant execution, ideal for quick tasks or integrating shell scripts into your workflows.

Example Usage

Imagine you want to fetch the current weather in Chicago using the curl command. The following Prefect CLI command does just that:

prefect shell watch "curl http://wttr.in/Chicago?format=3"

This command makes a simple request to wttr.in, a console-oriented weather service, and prints the weather conditions for Chicago.

Benefits

  • Immediate Feedback: Execute shell commands instantly within the Prefect framework for immediate results.
  • Easy Integration: Seamlessly blend external scripts or data fetching into your data workflows.
  • Visibility and Logging: Leverage Prefect's logging to track the execution and output of your shell tasks.

Deploying with serve

When you need to run shell commands on a schedule, the serve command creates a Prefect deployment for regular execution, streamlining task automation.

Example Usage

To set up a daily weather report for Chicago at 9 AM, you can use the serve command as follows:

prefect shell serve "curl http://wttr.in/Chicago?format=3" --flow-name "Daily Chicago Weather Report" --cron-schedule "0 9 * * *" --deployment-name "Chicago Weather"

This command schedules a Prefect flow to fetch Chicago's weather conditions daily, providing consistent updates without manual intervention.

Benefits

  • Automated Scheduling: Schedule shell commands to run automatically, ensuring critical updates are generated and available on time.
  • Centralized Workflow Management: Manage and monitor your scheduled shell commands alongside Prefect flows for a unified workflow overview.
  • Configurable Execution: Tailor execution frequency, concurrency limits, and other parameters to suit your project's needs and resources.

Next Steps

With the watch and serve commands at your disposal, you're ready to incorporate shell command automation into your Prefect workflows. Start with straightforward tasks like observing cron jobs and expand to more complex automation scenarios to enhance your workflows' efficiency and capabilities.

For more insights into Prefect's features and best practices, visit the Prefect documentation.