What is the best way to traverse and select/copy specific texts using Selenium?

This example an store all span class of "server-error" in an array, but I am having difficulty progressing beyond this point.


Can I add the value "123456" to a text file for each "server-error" I find?

I am new to this, and have looked around but cannot find a clear answer. I would be grateful for any help!

Code:

            <td>
                <label><input type="text" value="123456" name="specificNum"></label>

            </td>

            <td>
                <label><input type="text" value="1" name="allowIn"></label>

            </td>


            <td>
                        <span class="server-error">
                            Invalid Number
                        </span>       
            </td>

        <td class="centered"><a href="#" class="deleteRow">Remove</a></td>