adjoin

#!/usr/bin/env ruby
# Andy's Join: join lines in streams by separator.

require 'optparse'

# List of single character escape sequences
ESCAPES = {
  "\\\\" => "\\",
  '\a' => "\a",
  '\b' => "\b",
  '\e' => "\e",
  '\f' => "\f",
  '\n' => "\n",
  '\r' => "\r",
  '\s' => "\s",
  '\t' => "\t",
  '\v' => "\v",
}

# There has to be a better way to do this.
def apply_backslash_escapes(string)
  string = string.dup

  string.gsub!(/\\(\\|[abefnrstv]|0\d{1,3}|x\h{1,2}|\d{1,3})/) do |matched|
    captured = $1
    if ESCAPES.include?(matched)
      ESCAPES.fetch(matched)
    else
      if captured =~ /\A\d{1,3}\z/
        num = Integer(captured, 8)
        num.chr
      else
        case captured[0]
        when '0'
          num = Integer(captured[1..-1], 8)
          num.chr
        when 'x'
          num = Integer(captured[1..-1], 16)
          num.chr
        else
          raise "Unexpected escape: #{matched.inspect}"
        end
      end
    end
  end

  string
end

def adjoin(sep, *streams)
  first_stream = true

  streams.each do |stream|
    if first_stream
      first_stream = false
    else
      print sep
    end

    begin
      print stream.readline.chomp
    rescue EOFError
      # ignore
    end
    stream.each_line do |line|
      print sep
      print line.chomp
    end
  end

  print "\n"
end

def main
  options = {}
  optparse = OptionParser.new do |opts|
    opts.banner = <<-EOM
usage: #{File.basename($0)} [OPTIONS] SEPARATOR [FILE...]

Join each line in each FILE by SEPARATOR. If no FILE is not given, read from
standard input.

For example:

  $ seq 1 10 | adjoin ,
  1,2,3,4,5,6,7,8,9,10

  $ seq 1 5 | adjoin -e '\\t'
  1\t2\t3\t4\t5

  $ adjoin - 1to5.txt 6to10.txt
  1-2-3-4-5-6-7-8-9-10

Options:
    EOM

    opts.on('-h', '--help', 'Display this message') do
      puts opts
      exit
    end

    opts.on('-e', '--escape',
            'Enable interpretation of backslash escapes (buggy)') do
      options[:escapes] = true
    end

    opts.on('-0', '--null', 'Use a separator of NUL') do
      options[:null] = true
    end
  end

  optparse.parse!

  if options[:null]
    sep = "\0"
  else
    sep = ARGV.shift
  end

  if sep.nil?
    puts optparse
    exit 1
  end

  if options[:escapes]
    sep = apply_backslash_escapes(sep)
  end

  if ARGV.empty?
    streams = [STDIN]
  else
    streams = ARGV.map {|filename|
      if filename == '-'
        STDIN
      else
        File.open(filename, 'r')
      end
    }
  end

  adjoin(sep, *streams)

  0
end

if $0 == __FILE__
  exit main
end