How to combine files using cat?

Since cat stands for concatenate (which means "link together"), combining files is one of its primary jobs!

To combine files, you use the > (redirection) operator. This operator takes the output that would normally show up on your screen and sends it into a file instead.

Here are the most common ways to do it:

1. Combine two files into a new third file

If you have file1.txt and file2.txt and want to merge them into combined.txt:

cat file1.txt file2.txt > combined.txt

The order matters: file1.txt will appear first in the new file.

2. Append one file to the end of another

If you want to take the contents of file2.txt and add them to the bottom of file1.txt (without creating a new file), use >>:

cat file2.txt >> file1.txt

Note: Using > (single) overwrites the file, while >> (double) appends to the end.

3. Combine many files using a wildcard

If you have a dozen text files and want to merge them all:

cat *.txt > all_files_merged.txt

Try it yourself!

While you are in the terminal, you can try this quick test:

1. echo "Hello" > part1.txt
2. echo "World" > part2.txt
3. cat part1.txt part2.txt > full.txt
4. cat full.txt

You'll see that full.txt now contains both words! Does that help explain how it works?