CSV to key, values concat

csvconcat.rb

# Example
# READING FILE(CSV key,value format)
# k1,v1
# k1,v2
# k2,v3
# INTO
# k1  v1,v2
# k2  v3

# File open
f = File.open('concat.csv')
a = {}

f.each_line do |line|
  s = line.split(',')
  a[s[0]] = [] if a[s[0]].nil?
  a[s[0]].push(s[1])
end

f.close

# File out
o = File.open('concat_result.out', 'w')
a.map { |k,v| o.puts k + "\t" + (v.each {|e| e.strip!}).join(","))}
o.close