Why can't sudo redirect stdout to /etc/file, but sudo 'nano' or 'cp' can?

Question

Why does redirection, using sudo give me an error for the following commands?

$ sudo printf "foo" >/etc/file
bash: /etc/file: Permission denied

$ sudo printf "foo" ~/file; cat ~file >/etc/file 
bash: /etc/file: Permission denied

...yet I have no such problem when I use an editor, or cp.
I don't think I've ever tried this before, so I don't know if there is something haywire on my system, or if this is normal. It seems a bit restrictive to be normal, but(?) maybe it is intended to be restrictive... (using Ubuntu)

Solution

It is normal. The file after the > is not open by the process running under sudo, but by the shell, which isn't. Try this instead:

printf "foo" | sudo tee /etc/file

Comments

[Gilles 'SO- stop being evil']

Redirecting stdout to a file you don't have write permission on

[Peter.O]

Got it, thanks.. so this works too, sudo sh -c 'printf "foo" >/etc/file'

[Peter.O]

Also, as mentioned in the Q/A linked to by Gilles comment, tee -a caters for appending to a file...