is there a way to type the "@" sign in lstlisting? I have tried just putting @ or \@ but both don't seem to work:

@testing
123


or

\@testing
123


it just outputs

testing123

-
Welcome to TeX.sx! Please add a minimal working example (MWE) that illustrates your problem. It will be much easier for us to reproduce your situation and find out what the issue is when we see compilable code, starting with \documentclass{...} and ending with \end{document}. –  Marco Daniel Apr 25 '13 at 18:15
If you add an MWE, we can reopen this question as it will be useful to other users of the site. –  Charles Stewart Apr 26 '13 at 6:58
See also tex.stackexchange.com/questions/12768/… - this is close to a duplicate, although if you don't know what is going on, the difference in the character that manifests the problem will make them look different. –  Charles Stewart Apr 26 '13 at 7:08
The problem was that I had a escapeinside={@}{@} in my \lstset settings, so the @ symbol did not behave as I expected. This can be solved by changing that command so that other delimiters are used.