Does this write to stdout or stdin?

Question

If I type the following command in Linux:

cat textfile

The contents of textfile is displayed. What is cat actually writing to? Is it writing to stdout or stdin?

Answer 1

It's writing to stdout.

You can check this by trying the following:

cat textfile > stdout.log 2> stderr.log

You should find that all the output goes to stdout.log, not stderr.log.