How to return the substring of a string between two strings in Ruby?

Question

How would I return the string between two string markers of a string in Ruby?

For example I have:

• input_string
• str1_marker

Answer 1

input_string = "blahblahblahSTARTfoofoofooENDwowowowowo"
str1_markerstring = "START"
str2_markerstring = "END"

input_string[/#{str1_markerstring}(.*?)#{str2_markerstring}/m, 1]
#=> "foofoofoo"

or to put it in a method:

class String
  def string_between_markers marker1, marker2
    self[/#{Regexp.escape(marker1)}(.*?)#{Regexp.escape(marker2)}/m, 1]
  end
end

"blahblahblahSTARTfoofoofooENDwowowowowo".string_between_markers("START", "END")
#=> "foofoofoo"

Answer 2

Just split it twice and get the string between the markers:

input_string.split("str1_markerstring").last.split("str2_markerstring").first

Answer 3

Here's some alternate ways to do what you want, that are how I'd go about it:

s = "Charges for the period 2012-01-28 00:00:00 to 2012-02-27 23:59:59:<br>\nAny Network Cap remaining: $366.550<br>International Cap remaining: $0.000"  # => "Charges for the period 2012-01-28 00:00:00 to 2012-02-27 23:59:59:<br>\nAny Network Cap remaining: $366.550<br>International Cap remaining: $0.000"

dt1, dt2 = /period (\S+ \S+) to (\S+ \S+):/.match(s).captures  # => ["2012-01-28 00:00:00", "2012-02-27 23:59:59"]
dt1                                                            # => "2012-01-28 00:00:00"
dt2                                                            # => "2012-02-27 23:59:59"

This is using "period" and "to" and the trailing ":" to mark the begin and end of the range to be searched for, and grabbing the non-whitespace characters that signify the date and time in each datetime stamp.

Alternately, using "named-captures" predefines the variables:

/period (?<dt1>\S+ \S+) to (?<dt2>\S+ \S+):/ =~ s  # => 16
dt1                                                # => "2012-01-28 00:00:00"
dt2                                                # => "2012-02-27 23:59:59"

From that point, if you want to break down the values returned you could parse them as dates:

require 'date'
d1 = DateTime.strptime(dt1, '%Y-%m-%d %H:%M:%S')  # => #<DateTime: 2012-01-28T00:00:00+00:00 ((2455955j,0s,0n),+0s,2299161j)>
d1.month                                          # => 1
d1.day                                            # => 28

Or you could even use sub-captures:

matches = /period (?<dt1>(?<date1>\S+) (?<time1>\S+)) to (?<dt2>(?<date2>\S+) (?<time2>\S+)):/.match(s)
matches # => #<MatchData "period 2012-01-28 00:00:00 to 2012-02-27 23:59:59:" dt1:"2012-01-28 00:00:00" date1:"2012-01-28" time1:"00:00:00" dt2:"2012-02-27 23:59:59" date2:"2012-02-27" time2:"23:59:59">
matches['dt1']   # => "2012-01-28 00:00:00"
matches['date1'] # => "2012-01-28"
matches['time2'] # => "23:59:59"

This is all documented in the Regexp documentation.