cat — print file contents

💬 "cat command"

• Concept: Prints file contents to the screen as-is. It is the fastest way to check short configuration files.
• Output structure: The entire file is printed at once. It is unsuitable for large log files, so use less or tail.
• Practical recommendation: Use cat -n to add line numbers so you can point out and share the specific line that caused an issue.
• Left column: Not applicable — file contents are printed continuously as-is.
• Right column: Not applicable — if multiple files are provided, they are concatenated and printed in order.

3 Essential Command Combinations

• cat file — View file contents
• cat -n file — View with line numbers
• cat conf.d/*.conf — View multiple configuration files concatenated

There are also some options worth knowing.

• For long files, open them with less file to scroll
• If you only need the end, use tail -n 20 file

💬 "Give me a real-world example using a common combination"

Scenario: Quickly checking a changed configuration file with line numbers.

Step 1: View with line numbers

View the entire configuration with line numbers.

cat -n nginx.conf

Step 2: Check the last part

Check the recently added configuration.

tail -n 10 nginx.conf

Step 3: Concatenate multiple fragments

View fragment files together.

cat -n conf.d/*.conf

Actual output screen

This is an example screen showing configuration file contents with cat -n.

!cat command output: configuration file contents displayed with line numbers

Live production server

Source (HTML): https://games.aidebatehub.com/programs/linux/filesystem/cat.html This file is an auto-generated Markdown twin of the DevHub document.