How to prevent output for a shell script command

Question

What does tee do and is it possible to run this command in a alternative way with suppressing the output?

#!/bin/bash
echo "deb https://apt.dockerproject.org/repo ubuntu-xenial main" | sudo tee /etc/apt/sources.list.d/docker.list

Answer 1

The command

echo "deb https://apt.dockerproject.org/repo ubuntu-xenial main" | sudo tee /etc/apt/sources.list.d/docker.list

is an indirect way of saying:

echo "deb https://apt.dockerproject.org/repo ubuntu-xenial main" > /etc/apt/sources.list.d/docker.list

as root.

You see the output on the terminal because of the tee command.

You can rewrite it as below, to suppress the output, while running as non-root user:

echo "deb https://apt.dockerproject.org/repo ubuntu-xenial main" | sudo sh -c "cat > /etc/apt/sources.list.d/docker.list"

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See also:

• How do I use sudo to redirect output to a location I don't have permission to write to?

• https://askubuntu.com/questions/230476/when-using-sudo-with-redirection-i-get-permission-denied