rcat: cat(1) partial implementation in ruby (passes https://gist.github.com/1293709)

rcat

#!/usr/bin/env ruby

require 'optparse'

options = {}

OptionParser.new do |opts|
  opts.on('-n') { options[:number_all_lines] = true }
  opts.on('-b') { options[:number_nonblank_lines] = true }
  opts.on('-s') { options[:squeeze_blank_lines] = true }
  begin
    opts.parse!
  rescue OptionParser::ParseError => e
    STDERR.puts "rcat: #{e.message}", "usage: rcat [-bns] [file ...]"
    exit 1
  end
end

def number_lines(text)
  index = 0
  text.each_line.map do |line|
    "#{(index += 1).to_s.rjust(6)}\t#{line}"
  end.join
end

def number_nonblank_lines(text)
  index = 0
  text.each_line.map do |line|
    if line == "\n"
      line
    else
      "#{(index += 1).to_s.rjust(6)}\t#{line}"
    end
  end.join
end

def squeeze_blank_lines(text)
  text.each_line.with_object([]) do |line, ary|
    ary << line unless [line, ary.last].all? { |i| i == "\n" }
  end.join
end

begin
  output = ARGF.read
rescue Errno::ENOENT => e
  STDERR.puts "rcat: #{e.message}"
  exit 1
end

options[:number_all_lines] = false if options[:number_nonblank_lines]

output = squeeze_blank_lines output if options[:squeeze_blank_lines]
output = number_nonblank_lines output if options[:number_nonblank_lines]
output = number_lines output if options[:number_all_lines]

print output