Input/Output Redirection (>, >>, <)
Master redirecting command output to files and using files as input for commands, enhancing script flexibility.
Input/Output Redirection (>, >>, <) is a free DevOps Bootcamp lesson on CoddyKit. This is lesson 2 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the DevOps Bootcamp learning path, and your progress syncs across the web and the CoddyKit app. The DevOps Bootcamp course includes 4 lessons in total.
What is I/O Redirection?
In Linux, commands often produce output or require input. Input/Output (I/O) redirection lets you change where a command gets its input from or sends its output to.
Instead of just seeing output on your screen (the terminal), you can save it to a file, or even feed a file's content directly into another command.
Understanding Standard Streams
Every Linux command interacts with three "standard" data streams:
- Standard Input (STDIN): Where a command expects to receive input (usually your keyboard).
- Standard Output (STDOUT): Where a command sends its normal output (usually your screen).
- Standard Error (STDERR): Where a command sends error messages (also usually your screen).
Redirection allows us to change these default destinations or sources.
Capturing Output with '>'
The > operator is used to redirect Standard Output (STDOUT) from a command to a file. Instead of printing to the screen, the command's output will be written into the specified file.
Important: If the file already exists, > will overwrite its entire content with the new output. Be careful not to accidentally delete important data!
Example: Saving Command Output
Let's save the output of the ls -l command into a file named my_files.txt. Then, we'll view the file's content using cat.
ls -l > my_files.txt
cat my_files.txtAdding to a File with '>>'
Sometimes you don't want to overwrite a file; you want to add new content to the end of it. That's where the >> operator comes in!
>> redirects Standard Output (STDOUT) to a file, but if the file already exists, it will append the new output to the end of the file, preserving existing content.
Example: Appending to a Log
First, create a simple file. Then, use >> to add another line to it. Observe how the original content is kept.
echo "First line of log." > app_log.txt
echo "Second line added." >> app_log.txt
cat app_log.txtHandling Errors with '2>'
What about error messages? They go to Standard Error (STDERR). To redirect STDERR to a file, we use the file descriptor 2 followed by the > operator: 2>.
This is extremely useful for logging errors without cluttering your main output or for debugging scripts.
Example: Logging Error Messages
Let's try to list a directory that doesn't exist. The error message will normally show on screen. We'll redirect it to errors.log instead.
ls /this/path/does/not/exist 2> errors.log
echo "Command finished. Check errors.log."
cat errors.logProviding Input with '<'
The < operator is used to redirect Standard Input (STDIN). Instead of a command waiting for you to type input from the keyboard, it will read its input directly from the specified file.
This is powerful for automating tasks where a command expects a lot of input, or when you want to process a file's content directly.
Example: Sorting from a File
We'll create a file with unsorted names, then use the sort command to read its input from that file using <.
echo -e "Charlie\nAlice\nBob" > names.txt
sort < names.txtQuick Check: Redirection
You've learned about redirecting standard output, appending output, handling errors, and providing input from files. Let's test your understanding.
Recap: I/O Redirection Power
Great job! You've mastered the fundamentals of I/O redirection in Linux.
>redirects STDOUT, overwriting files.>>redirects STDOUT, appending to files.2>redirects STDERR, capturing error messages.<redirects STDIN, allowing commands to read from files.
These operators are incredibly powerful for scripting, logging, and automating tasks. Keep practicing!
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Frequently Asked Questions
Is the “Input/Output Redirection (>, >>, <)” lesson free?
Yes — any 3 lessons of the DevOps Bootcamp learning path, including “Input/Output Redirection (>, >>, <)”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The DevOps Bootcamp course includes 4 lessons in total.
What will I learn in “Input/Output Redirection (>, >>, <)”?
Master redirecting command output to files and using files as input for commands, enhancing script flexibility. You practise DevOps Bootcamp with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start DevOps Bootcamp?
No prior experience is required. DevOps Bootcamp on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 4.
How long does the “Input/Output Redirection (>, >>, <)” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this DevOps Bootcamp lesson?
Yes. Every DevOps Bootcamp lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Managing Processes (ps, top, kill)
- Input/Output Redirection (>, >>, <)
- Piping Commands (|)
- Background Jobs & Job Control