1) To validate an Integer number (can be positive or negative) your regular expression will be
2) To validate a decimal number (can be positive or negative) your regular expression will be as below. This will work for Integer number handling too.
The above regular expression will work with Perl/PHP/Python/Ruby. I didn't tested with java/.NET and other languages.
For PHP use preg_match() function.
For Python use the function findall from regular expression class. that means re.findall()
For Ruby and Perl, use it like, variable_name =~ /REGEXP HERE/