1. stdout (Standard Out)

As you continue to learn Linux, you've seen how commands produce output. This brings us to the important topic of I/O (input/output) streams, specifically standard output or stdout. Let's explore this concept by running the following command:

echo Hello World > peanuts.txt

After running this, you will find a new file named peanuts.txt in your current directory. If you view its contents, you'll see the text "Hello World". Let's break down what happened.

Understanding Standard Output (stdout)

First, consider the command without the special character:

echo Hello World

By default, many commands send their results to stdout, which is your terminal screen. This is why echo Hello World displays the text directly in your shell. Processes use I/O streams to receive input (standard input or stdin) and send output. I/O redirection allows us to change this default behavior, giving us greater control over our data.

Redirecting stdout with >

The > character is a redirection operator. It intercepts the data heading to stdout and sends it to a new destination.

>

In our example, it sends the output of echo Hello World to a file instead of the screen. If the file doesn't exist, it will be created. Be careful, as if the file already exists, this operator will completely overwrite its contents.

Appending stdout with >>

What if you want to add to a file without erasing its contents? For that, we use the >> operator.

echo Hello World >> peanuts.txt

This operator appends the output to the end of the specified file. If the file doesn't already exist, it will be created, just like the > operator. Mastering stdout redirection is a fundamental step in your Linux journey.