Why is STDERR redirected to STDOUT

Question

I noticed that we have mainly 3 file streams. They are STDIN, STDOUT and STDERR.. My question is why is STDERR redirected to STDOUT?

Answer 1

stderr is not redirected to stdout. Both streams are only connected to the same device (the current screen or terminal) by default.

You can redirect them to different files:

$ command > stdout.log 2> stderr.log

In order to actually redirect stderr to stdout, you have to issue:

$ command 2>&1

Answer 2

It is not; it just happens that both stdout and stderr are typically mapped to the same output stream (usually the console). If you redirect stdout to a file for example you will find that stderr remains directed to the console.

The important point is that they are independently redirectable.