Reads a rails log and extracts the given parameters, prints CSV.

rails_log_parameters.rb

#!/usr/bin/env ruby

file = ARGV.shift
parameters = ARGV

unless file && !parameters.empty?
  puts <<-end_usage
  Usage #{$0} logfile param [param, ...]
    Reads a rails log and extracts the given parameters, prints CSV.
    Useful to include [action, controller] in parameters.
  end_usage
  exit
end

STDOUT.puts (%w[timestamp] + parameters).join(',')
pattern = %r!(^[\S]+)? .*Parameters.*"(?:#{parameters.join('|')})"!

File.open file do |f|
  f.each do |line|
    if line =~ pattern
      row = [$1]
      parameters.each do |attr|
        line =~ %r!"#{attr}"=>"([^"]*)"!
        row << $1
      end
      STDOUT.puts row.join(',')
    end
  end
end