I think this is probably easy but I don't have the time to learn how to do it.
In a html file, I have a certain class of paragraph, let´s say:
<p class="footnote"></p>
The "p" tag is always followed by numbers, which increase by one in every instance. Let's say the first number is "43". I want the series of numbers to start from 1, so I need to substract 42 from all paragraphs.
For example, I would want to go from:
<p class="footnote">43. Lorem</p>
<p class="footnote">44. Ipsum</p>.
<p class="footnote">45. Dolor</p>.
to
<p class="footnote">1. Lorem</p>
<p class="footnote">2. Ipsum</p>.
<p class="footnote">3. Dolor</p>.
How can I do it?
If you're looking for a regex that'll handle <p class="footnote">43. Lorem</p> the answer is don't parse HTML with regex.
Assuming you've extracted the string 43. Lorem from a tag and you want to get a number out then it depends on your requirements:
To find any number: \d+
To find any number at the beginning: ^\d+
To find any number followed by a period: \d+\.
A more complete solution will require more details about the problem including the programming language you want to use.