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Re: [tlug] Accessing microphone

On 08/05/06, Dave M G <> wrote:$ sudo generate-modprobe.conf > /etc/modprobe.conf
bash: /etc/modprobe.conf: Permission denied

How can I be denied permission if I'm doing it with "sudo"? It didn't
even ask me for my password?

This is a great example to illustrate how a shell works. When you type
the above command, the shell interprets it as:

1. Run the "sudo generate-modprobe.conf" command, then
2. Redirect its output to the "/etc/modprobe.conf" file

sudo ensures that the "generate-modprobe.conf" file runs as root, but
the shell, which is redirecting the output of the command to a file,
is still running as a non-privileged user, namely, you.

There are (at least) two ways around this. One would be to redirect
the output of the command to a file to which you have write
permission, then move it to its proper location, i.e.

generate-modprobe.conf > /tmp/modprobe.conf
sudo mv /tmp/modprobe.conf /etc/modprobe.conf

Or, you could use the magic of tee(1) and Unix pipes:

generate-modprobe.conf | sudo tee /etc/modprobe.conf

Read the manpage of tee(1) to see why this works. :)


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