csv_parser.rb

#!/bin/env ruby

STOP_QUOTED_RE = /(?:[^"]|"{2})(",)/
STOP_NORMAL_RE = /(,)/

# returns [chunk, rest], rest is nil at the end
def read_chunk(line)
  quoted  = line[0] == '"'
  start   = quoted ? 1 : 0

  stop_re    = quoted ? STOP_QUOTED_RE : STOP_NORMAL_RE
  stop_match = stop_re.match line

  # no match means end of line or badly formatted
  return [line, nil] if stop_match.nil?

  stop   = stop_match.offset(1)[0] - 1
  nstart = stop_match.offset(1)[1]

  # otherwise it's thte start to match begin, match end to end
  chunk = line[start..stop]
  rest  = line[nstart..-1]
  [chunk.gsub(/""/, '"'), rest]
end

# returns an array of chunks for a line
def read_line(line)
  results = []
  until line.nil?
    chunk, line = read_chunk(line)
    results << chunk
  end

  results
end

$stdin.each_line do |line|
  row = read_line(line)
  puts row.join("|")
end

## ruby csv_parser.rb
"Alexander ""Alex""",Mendoza,"San Francisco",CA,4
Alexander "Alex"|Mendoza|San Francisco|CA|4
Chris,Hitchens,Denver,CO,40
Chris|Hitchens|Denver|CO|40
"""""Alex"""" Ander",Jones,"""Twin Cities""",MN,5
""Alex"" Ander|Jones|"Twin Cities"|MN|5