Run shell command and send output to file?

Question

I need to be able to modify my openvpn auth file via a php script. I have made my http user a no-pass sudoer, as this machine is only available within my home network.

Answer 1

Instead of running an entire shell process as root, which is arguably unsafe, you can run the copy as root:

(with bash):

sudo cp <(echo "$username") /etc/openvpn/auth.txt

(should work with any shell):

echo "$username" | sudo dd of=/etc/openvpn/auth.txt