Standard Streams and File Descriptors

At the end of the last lesson, you got an introduction to standard streams and file descriptors, along with how to redirect output.

In this lesson, you’ll dive deeper, learning how redirection works under the hood. In addition, you will learn about the three different kinds of standard streams. In Unix systems, processes commonly start with three special kinds of streams called standard streams: standard input (which is used to receive input), standard output (where command output goes), and standard error (where error messages go).

You will also learn how the computer sees standard streams as non-negative integers called file descriptors. Many commands take input not only from the filenames that are passed as arguments to them, but also from standard input.

As you work through each concept, you will be given an opportunity to apply what you’ve learned so far. The terminal inside of the lesson includes answer checking so you can ensure that you’ve fully mastered each concept before learning the next concept. And by the time you reach the end of this lesson, you’ll have a solid grasp of the command line skills that are critical to working efficiently as a data analyst or data scientist.


  • What standard streams are
  • What file descriptors are
  • How to redirect output

Lesson Outline

  1. Standard Streams
  2. Recap
  3. Redirecting Two Streams
  4. File Descriptors
  5. A New Point of View
  6. Duplicating File Descriptors
  7. Order of Redirections
  8. Standard Input
  9. Redirecting Standard Input
  10. Next Steps
  11. Takeaways

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