An editor is just that; a tool to edit files. In the case of nano, its a 'plain-text' editor ie you can't edit binary files or eg OO docs etc.
See also vi/vim, gedit etc etc; Linux has a lot(!) of editors to choose from
The 'simplest' storage format would probably be a flat file eg
In order to use this, you need a unique identifier value for reach 'record' (line) to act as a key (index) so you only pull out one record for a request.
In your case, I'm guessing the email, in which case it should be the first field in each record.
You could use the 'cut' cmd http://linux.die.net/man/1/cut
or (more powerful) awk http://www.grymoire.com/Unix/Awk.html
Here are some good bash (scripting lang) refs/tutorials; bookmark and read
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