regex that matches any positive or negative numeric value but no characters or mixed strings
===

I haven't used regular expressions till now, but I need a regex that matches a string representing a positive or negative numeric value like

234

-8

3.346

-564.4

It should NOT match any text or mixtures of characters (<>#?_...), numbers and text like

abc

.-.

<11.45

amount111.43

345.654.33

