7. cat

After learning to navigate the filesystem, the next step is to view the contents of files. A fundamental and versatile tool for this is the linux cat command. The name cat is short for "concatenate," which hints at its ability to link files together.

Viewing File Contents

The most basic use of the cat command is to display the content of a single file directly in your terminal.

cat myfile.txt

This command will print the entire content of myfile.txt to the screen. While this is perfect for short configuration files or text snippets, it's not ideal for viewing large files, as the text will scroll by very quickly. We will cover tools better suited for large files in a later lesson.

Concatenating Files

True to its name, cat can combine, or concatenate, multiple files and display their combined output. The cat linux utility reads the files in the order they are provided and prints them sequentially.

cat dogfile birdfile

This command will first display the contents of dogfile, immediately followed by the contents of birdfile.

Creating Files with Redirection

You can also use cat with the output redirection operator (>) to create new files. The linux cat > combination is a quick way to write text into a file directly from your terminal.

cat > newfile.txt

After running this command, you can type your text. Press Ctrl+D on a new line to save and exit. This will create newfile.txt with the text you entered. Be careful, as using > on an existing file will overwrite it completely.

Common cat Command Options

The cat command has several options to modify its behavior. Here are a couple of common ones:

• -n: This option numbers all output lines, starting from 1.
• -b: This option numbers only the non-empty output lines.

For a complete list of functionalities, you can always refer to the cat manual linux page by typing man cat in your terminal.