re = /(\d+)\s+([A-Z]+)(\d+)\s+(\w+)/
str = '6876786786 GFS8978976 I
6786786767 DDF78676 I
4343245443 SBSSK67676 I
8393372263 SBSSK56565 I
6545434347 DDF7878333 I
6757650000 SBSSK453 I'
subst = '$1+$2+$3+$4'
result = str.gsub(re, subst)
# Print the result of the substitution
puts result
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html