re = /ATEAM-[0-9]+(?=.*?#finish)/im
str = 'ATEAM-3121 ATEAM-31 123 ATEAM-32 #finish \\n ATEAM-3211 \\n ATEAM-51 ATEAM-52 ATEAM-53 12345677 #finish ATEAM-1000'
# Print the match result
str.scan(re) do |match|
puts match.to_s
end
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