What is the question mark inside this regex doing?

[John Merlino]

I thought the ? matches zero or one occurrence of a pattern. However in this example:

def show_regexp(string, pattern)

  match = pattern.match(string)

  if match

    "#{match.pre_match}->#{match[0]}<-#{match.post_match}"

  else

    "no match"

  end

end

a = "The moon is made of cheese"

show_regexp(a, /\s.*?\s/) #=> The-> moon <-is made of cheese

What exactly is the ? doing?

[Robert Walker]

'John Merlino' via Ruby on Rails: Talk wrote in post #1155178:

*? -- 0 or more, lazy. Matches will be as small as possible.

/\s.*\s/.match(searchText) (not lazy)

/\s.*?\s/.match(searchText) (lazy)

/\s.*\s/ (not lazy)
The-> moon is made of <-cheese (1 match)

/\s.*?\s/ (lazy)
=> The-> moon <-is-> made <-of cheese (2 matches)

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