Ruby code to parse and combine text files

I use this ruby code to parse several tab-delimitted text files that contain individual raters’ perceptions of a target (in this case a video). The rater id is embedded in the filename. The target video number is also embedded in the filename.

#! /usr/bin/env ruby

out = Dir.glob('*.txt')

# open the file to write to and add the column headers
columns = "grouptratertmintengagetpreparetdivergetconvergetexecutetcentralizetattentivettonetactivationn""./all_ratings.txt", 'w') { |f| f.write(columns) }

out.each do |filename|
rater = filename.split('.')[0].split('_')[0]
group = filename.split('.')[0].split('_')[1]

# Assign a number for the rater
case rater.downcase
when "rater1"
rater_id = 1
when "rater2"
rater_id = 2
when "rater3"
rater_id = 3
when "rater4"
rater_id = 4
puts "rater: " + rater + "(#{rater_id})" + " group: " + group

# Open the file
f =, "r").read

# Split by lines - This will make sure that the end of line from Mac Classic is n
str = f.gsub!(/rn?/, "n").split("n")

# Identify the line number that starts the data entry for this file by finding a specific expression in the text of the file

linenum = 0
exp = "- Low marked by sluggishness"
line = str[linenum]
puts line
until line.include?(exp)
line = str[linenum]
linenum += 1

linenum.upto(linenum+30) do |currentline|
min = (currentline-linenum)+1
# add the rater_id and the group_id to the line
line = group.to_s + "t" + rater_id.to_s + "t" + str[currentline] + "n""./all_ratings.txt", 'a') { |f| f.write(line) }