Automating Enter keypress not working for Linux Mint 15 - linux

Question

I've got this post installation script I made for users of Linux Mint 14 (and also usable on Ubuntu 12.10) and now I'm testing it for Linux Mint 15 and the 'echo -ne "\n" | sudo add-apt-repository ppa:some-ppa-to-add' command isn't working on Linux Mint 15, but still works on Mint 14. I want to update this script for the new version of Linux Mint.
Here's a link to my post install scipt: The Minty Developer
The output for Mint 14 looks like this:
$ echo -ne "\n" | sudo add-apt-repository ppa:apt-fast/stable
You are about to add the following PPA to your system:
This PPA contains tested (stable) builds of apt-fast.
More info: https://launchpad.net/~apt-fast/+archive/stable
gpg: keyring `/tmp/tmpddxueh/secring.gpg' created
gpg: requesting key CA8DA16B from hkp server keyserver.ubuntu.com
gpg: /tmp/tmpddxueh/trustdb.gpg: trustdb created
gpg: key CA8DA16B: public key "Launchpad PPA for apt-fast" imported
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
OK
And here's the output on Mint 15:
$ echo -ne "\n" | sudo add-apt-repository ppa:apt-fast/stable
You are about to add the following PPA to your system:
This PPA contains tested (stable) builds of apt-fast.
More info: https://launchpad.net/~apt-fast/+archive/stable
And that's it. Nothing happens.
I've also tested doing just echo | ppa:some-ppa-to-add and it's the same results.
Can anyone help me figure out how to make this line of code/command work so that the script can be updated for those interested in using it with a new version of their system?
Thank you.

Answer 1

You could use add-apt-repository --yes but you are overriding a system-wide security policy by answering that question.
You don't say who the user is; I would be annoyed if your script did that for me, but I'm not a typical end-user. I just looked at your script, and it is conversational enough generally. If it said something like
I'm going to add these packages from reasonably trustworthy sources and set them up so they will automatically update, etc., etc.
it would be more polite.
Added
There is an undocumented feature in add-apt-repository which allows you to override the question programmatically:
if (sys.stdin.isatty() and
not "FORCE_ADD_APT_REPOSITORY" in os.environ):
if options.remove:
print(_("Press [ENTER] to continue or ctrl-c to cancel removing it"))
else:
print(_("Press [ENTER] to continue or ctrl-c to cancel adding it"))
sys.stdin.readline()
Thus the bash sequence
export FORCE_ADD_APT_REPOSITORY=force
sudo add-apt-repository ppa:webupd8team/sublime-text-2
sudo add-apt-repository ...
should stop the questions. It will still show the noise
You are about to add the following PPA to your system:
Sublime Text 2 packages - the .deb will automatically download the
latest build from http://www.sublimetext.com/dev or beta from
http://www.sublimetext.com/2 (Adobe Flash Player installer - style).
More info and feedback:
http://www.webupd8.org/2011/03/sublime-text-2-ubuntu-ppa.html
http://www.webupd8.org/2012/03/sublime-text-2-ppa-separate-development.html
More info: https://launchpad.net/~webupd8team/+archive/sublime-text-2
but that is put on stdout so should be able to be sent to > /dev/null with errors still appearing on stderr.