Command line script to Parse CSV files

csv.rb

#!/usr/bin/env ruby

# How about an awesome command-line script
# that replaces your usage of "awk -F, ..."
# for like 99% of cases.
#
# Also, importantly, it supports CSV features
# like escaping commas when quoted
#
# Usage: csv.rb [options] <filename>
#    -c <column 1> <column 2> ...,    Specify the columns to print
#        --column
#    -d, --delimeter <delimeter>      Specify the delimeter when printing the columns back out (default: " ")
#

require 'rubygems'
require 'csv'
require 'optparse'

options = {}

options[:delimeter] = " "
options[:columns]   = []

optparse = OptionParser.new do |opts|
  opts.banner = "Usage: csv.rb [options] <filename>"

  opts.on( "-c",
           "--column <column 1> <column 2> ...",
           "Specify the columns to print"
  ) do |column_list|
    cols = []
    column_list.scan(/(\D)?(\d+)/).each do |d, n|
      case d
      when nil, ","
        cols << n.to_i
      when "-"
        cols.push *((cols.last + 1)..n.to_i).to_a
      end
    end
    options[:columns] = cols
  end

  opts.on( "-d",
           "--delimeter <delimeter>",
           "Specify the delimeter when printing the columns back out (default: \" \")"
         ) do |delimeter|
    options[:delimeter] = delimeter
  end
end

optparse.parse!

selection = options[:columns].empty? ? ->(r){ r } : ->(r){ r.values_at(*options[:columns]) }
read_csv  = ARGV.empty? ? ->(&block){ CSV($stdin){ |c| c.each{|r| block.call(r) } } } : ->(&block){ CSV.foreach(ARGV[0]){|r| block.call(r) } }

read_csv.call do |r|
  begin
    puts selection.call(r).join(options[:delimeter])
  rescue Errno::EPIPE
    break
  end
end