Ruby find string in file and print result

Question

It\'s been a very long time since I\'ve used ruby for things like this but, I forget how to open a file, look for a string, and print what ruby finds. Here is what I have:

Answer 1

File.open 'file.txt' do |file|
  file.find { |line| line =~ /regexp/ }
end

That will return the first line that matches the regular expression. If you want all matching lines, change find to find_all.

It's also more efficient. It iterates over the lines one at a time, without loading the entire file into memory.

Also, the grep method can be used:

File.foreach('file.txt').grep /regexp/

Answer 2

The simplest way to get the root is to do:

rake routes | grep root

If you want to do it in Ruby, I would go with:

File.open("config/routes.rb") do |f|
  f.each_line do |line|
    if line =~ /root/
      puts "Found root: #{line}"
    end
  end
end

Answer 3

Inside text you have the whole file as a string, you can either match against it using a .match with regexp or as Dave Newton suggested you can just iterate over each line and check. Something such as:

f.each_line { |line|
  if line =~ /string/ then
    puts line
  end
}