How can I gsub everything until the next empty line?

Question

Given this string:

bc.  some text
 more text
 even more

^ above here is the empty line

I want it to be:

<pre>
some text
more text
even more
</pre>

^ above here is the empty line

How can I regex for "starting from bc. until the first empty line"?

So far I got this:

# note that for some reason a direct .gsub! behaves
# differently/fails when using the block, so I use .gsub
textile_markup = textile_markup.gsub(/^bc.  .*^$/m) { |s| "<pre>#{s[5..(s.length)]}</pre>" }

Understandibly, this matches greedy until the very last empty line - instead of the first one. How can I make the ^$ part non-greedy?

Answer 1

str = 
"bc.  some text
more text
even more

^ above here is the empty line

bc.  some text
more text
even more

^ above here is the empty line"

puts str.gsub(/^bc\.  (.*?)\n\n/m, "<pre>\n\\1\n</pre>\n\n")

Output:

<pre>
some text
more text
even more
</pre>

^ above here is the empty line

<pre>
some text
more text
even more
</pre>

^ above here is the empty line

Explanation

? in .*? makes the star operator non greedy

/m modifier in the end makes dot match newlines

Answer 2

It can be done in one go, but it needs some preparation:

txt = <<DOC
bc.  some text
 more text
 even more

bc.  some text
 more text
 even more

DOC

TRANSFORMS = {"bc.  " => "<pre>\n",       # The 'bc.  should become <pre> followed by a line-end
              /^ /    => "",              # leading space should be eliminated
             "\n\n"   => "\n<\/pre>\n\n"} # empty line should be preceded by a closing pre-tag

re = Regexp.union(TRANSFORMS.keys)
puts txt.gsub(re, TRANSFORMS)

Output:

<pre>
some text
more text
even more
</pre>

<pre>
some text
more text
even more
</pre>