Ruby, regex to match tabs and replace with 2 spaces?

Question

Does anyone have a regex in ruby that can match and replace a tab with 2 spaces?

Answer 1

Couldn't be simpler:

str.gsub(/\t/, '  ')

Answer 2

If you want to expand tabs (which is a slightly different task than replacing tabs), then:

# This algorithm by Brian Candler ([email protected]) found on the
# org.ruby-lang.ruby-talk mailing list
# http://markmail.org/message/avdjw34ahxi447qk
# Date: 2003-5-31 13:35:09
# Subject: Re: expandtabs

def expand_tabs(s, tab_stops = 8)
  s.gsub(/([^\t\n]*)\t/) do
    $1 + " " * (tab_stops - ($1.size % tab_stops))
  end
end

p expand_tabs("\tfoo", 2)      # => "  foo"
p expand_tabs(" \tfoo", 2)     # => "  foo"
p expand_tabs("\t\tfoo", 2)    # => "    foo"

The reason expanding tabs is different than just replacing them is that a tab can represent a different number of characters depending upon which column it appears in. For example, if the tab stops are every 8 columns, then a tab in the first column should be replaced by 8 spaces, but one in the second column by 7 spaces, one in the third column by 6 spaces, and so on.