$ tty /dev/tty0
in user-space, cat process waits on it's stdin to receive input from /dev/tty0 file.
On listing non-existent file fff,
ls /fff > file1 ls cannot find file :file1 Access denied
Despite redirection of stdout to file1 instead of /dev/tty0, the error about, file does not exist, will display on /dev/tty0 through stderr file descriptor.
If stderr writes to /dev/tty0 similar to stdout, what is the purpose of stderr?
What was the idea behind, UNIX/Linux maintaining one more file descriptor stderr for writing error to /dev/tty0 ?