7.3. Bang (!) methods and “danger”
Ruby methods can end with an exclamation point (!), or bang. The bang has no significance to Ruby internally; bang methods are called and executed just like any other methods. But by convention, the bang labels a method as “dangerous”—specifically, as the dangerous equivalent of a method with the same name but without the bang.
Dangerous can mean whatever the person writing the method wants it to mean. In the case of the built-in classes, it usually means this method, unlike its nonbang equivalent, permanently modifies its receiver. It doesn’t always, though: exit! is a dangerous alternative to exit, in the sense that it doesn’t run any finalizers on the way out of the program. The danger in sub! (a method that ...
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