I am new to linux, and just beginning to learn bash. I am using Ubuntu 9.04, and would like to add repositories to /etc/apt/sources.list from the command line. Basically, I would like to do this:
sudo echo "[some repository]" >> /etc/apt/sources.list
However, even when I use sudo, I get this error:
bash: /etc/apt/sources.list: Permission denied
How do I avoid this error?
This does not quite belong here, but the answer is:
echo "[some repository]" | sudo tee -a /etc/apt/sources.list
The tee command is called as the superuser via sudo and the -a argument tells tee to append to the file instead of overwriting it.
Your original command failed, as the IO redirection with >> will be done as the regular user, only your echo was executed with sudo.
Calling a sudo subshell like
sudo sh -c 'echo "[some repository]" >> /etc/apt/sources.list'
works, too as pointed out by others.
One way to solve this is to do the redirection in a subshell:
sudo sh -c 'echo "[some repository]" >> /etc/apt/sources.list'
That way, the sh process is executed under sudo and therefore has the necessary privileges to open the redirected output to /etc/apt/sources.list.
The shell processes ">", "<", ">>" etc itself before launching commands. So the problem is that "sudo >> /etc/foo" tries to open /etc/foo for append before gaining privileges.
One way round this is to use sudo to launch another shell to do what you want, e.g.:
sudo sh -c 'echo "[some repository]" >> /etc/apt/sources.list'
Or alternatively:
echo "[some repository]" | sudo sh -c 'cat >> /etc/apt/sources.list'
A simpler approach may simply be to use sudo to launch an editor on the /etc/file :)
In Karmic, you can just use the add-apt-repository command, at least for PPAs.
For example:
sudo add-apt-repository ppa:docky
Better to use a separate file in /etc/apt/sources.list.d as explained in this other answer.