Why are exclamation marks used in Ruby methods?

Question

In Ruby some methods have a question mark (?) that ask a question like include? that ask if the object in question is included, this then returns a

Answer 1

!

I like to think of this as an explosive change that destroys all that has gone before it. Bang or exclamation mark means that you are making a permanent saved change in your code.

If you use for example Ruby's method for global substitutiongsub!the substitution you make is permanent.

Another way you can imagine it, is opening a text file and doing find and replace, followed by saving. ! does the same in your code.

Another useful reminder if you come from the bash world is sed -i has this similar effect of making permanent saved change.