Using regex to replace all spaces NOT in quotes in Ruby

I'm trying to write a regex to replace all spaces that are not included in quotes so something like this:

a = 4, b = 2, c = "space here"

would return this:

a=4,b=2,c="space here"

I spent some time searching this site and I found a similar q/a ( http://stackoverflow.com/questions/79968/split-a-string-by-spaces-in-python#80449 ) that would replace all the spaces inside quotes with a token that could be re-substituted in after wiping all the other spaces...but I was hoping there was a cleaner way of doing it.

From stackoverflow $pageUsers[$entry.posts[0].author].name

• I consider this very clean:

  mystring.scan(/((".*?")|([^ ]))/).map { |x| x[0] }.join
  

  I doubt gsub could do any better (assuming you want a pure regex approach).

  From Romulo A. Ceccon

• This seems to work:

  result = string.gsub(/( |(".*?"))/, "\\2")
  

  Gene T : if you get into single- and double-quoted strings, you need to match opening and closing quote marks
  From Borgar

• try this one, string in single/double quoter is also matched (so you need to filter them, if you only need space):

  /( |("([^"\\]|\\.)*")|('([^'\\]|\\.)*'))/
  

  From Senmiao Liu

• It's worth noting that any regular expression solution will fail in cases like the following:

  a = 4, b = 2, c = "space" here"
  

  While it is true that you could construct a regexp to handle the three-quote case specifically, you cannot solve the problem in the general sense. This is a mathematically provable limitation of simple DFAs, of which regexps are a direct representation. To perform any serious brace/quote matching, you will need the more powerful pushdown automaton, usually in the form of a text parser library (ANTLR, Bison, Parsec).

  With that said, it sounds like regular expressions should be sufficient for your needs. Just be aware of the limitations.

  rjmunro : What is the 'correct' solution for this case?
  From Daniel Spiewak

• Daniel,

  The space between double-quote and 'here' is NOT in quotes in your example.

  From Senmiao Liu