Matching numbers with regular expressions — only digits and commas

Question

I can\'t figure out how to construct a regex for the example values:

123,456,789
-12,34
1234
-8

Could you help me?

Answer 1

^-?    # start of line, optional -
(\d+   # any number of digits
|(\d{1,3}(,\d{3})*))  # or digits followed by , and three digits
((,|\.)\d+)? # optional comma or period decimal point and more digits
$  # end of line