`cat`: Reading Files

cat (concatenate) prints the full contents of a file to the terminal. It's the quickest way to read a short file without opening a text editor.

Basic usage

cat notes.txt

Output:

Remember to learn the terminal.
Practice every day.

The file's entire contents are printed and you're back at the prompt immediately.

cat can read multiple files in sequence:

cat file1.txt file2.txt

The output is both files concatenated together — which is where the name comes from.

cat is frequently the first command in a pipeline:

cat access.log | grep 404 | wc -l

This reads the log, filters for 404 errors, and counts the results.

Large files: cat prints everything. For a 1 GB log file, that's a lot of scrolling. Use head or tail instead.
Binary files: cat will print raw binary, garbling your terminal. Use file to check the type first.
Editing: cat is read-only. To edit a file, use a text editor like nano or vim.

cat > newfile.txt

This lets you type content and saves it to newfile.txt when you press Ctrl+D. But using echo with redirection is usually cleaner:

echo "hello world" > newfile.txt

Use cat to print the contents of notes.txt.