csv2md_table.rb

#!/usr/bin/env ruby
require 'csv'

body = if ARGV.length > 0
        ARGF.read
      else
        STDIN.read
      end

csv = CSV.new(body)

def wrap(cols, gap=nil)
  if gap
    cols = gap.map.with_index{|length, i|  sprintf("%-#{length}s", cols[i]) }
  end
  "|#{cols.join('|')}|"
end

gap = nil
while !csv.eof?
  row = csv.readline
   unless gap
     cols = row.to_a
     puts wrap(cols)
     gap = cols.map{|col| col.length }
     puts wrap(cols.map{|col| col.gsub(/./, '-') if col })
     next
   end
   puts wrap(row.to_a, gap)
end