I'm doing some HTML stripping using regular expressions (yes, I know, never parse HTML with regexes, but I'm just stripping it, and I also unfortunately cannot use any external libraries). I'm using a regex from the Regular Expressions Cookbook, and it has worked great, except I just ran into this problem:
In the string Bob Saget <bobs@aol.com>, my regex is matching the email as a tag.
So my question is, is the @ sign a valid XML or HTML tag character? (I'm not asking whether or not it is valid within an attribute; I know that it is) If it is not, I will be able to successfully exclude it in my regex.
I'm not sure where to look this up. I looked here and I think that says that in XML, the at-sign is not allowed in a tag; however, I would appreciate some concrete proof.
After another look at the XML Specification:
A tag consists of:
'<' Name (S Attribute)* S? '>'
A Name consists of:
NameStartChar (NameChar)*
A NameStartChar consists of:
":" | [A-Z] | "_" | [a-z] | [#xC0-#xD6] | [#xD8-#xF6] | [#xF8-#x2FF] | [#x370-#x37D] | [#x37F-#x1FFF] | [#x200C-#x200D] | [#x2070-#x218F] | [#x2C00-#x2FEF] | [#x3001-#xD7FF] | [#xF900-#xFDCF] | [#xFDF0-#xFFFD] | [#x10000-#xEFFFF]
A NameChar consists of:
NameStartChar | "-" | "." | [0-9] | #xB7 | [#x0300-#x036F] | [#x203F-#x2040]
The @ sign is U+0040
So the @ sign is not valid in a NameChar or a NameStartChar, and thus not valid in a Name.
来源：https://stackoverflow.com/questions/7065693/is-the-at-sign-a-valid-html-xml-tag-character