mvgsub

#!/usr/bin/env ruby
require 'fileutils'
include FileUtils

def usage
puts <<EOS
usage: #{$0} glob-pattern from to
  in all files matched by glob-pattern (classical shell
  glob pattern), replace from (ruby regex) with to (ruby
  substitution for gsub)

options:
  --help
  -h          display this help

  --pretend
  -p          show what replacements will be without
              actually moving files

example:
  mv trail-* 'trail-(.*)\.jpg' 'head-\\1.jpg'
EOS

end

files = Array.new
to    = nil
from  = nil

while ( arg = ARGV.pop )
  case arg
    when '--help', '-h'
      usage
      exit

    when '--pretend', '-p'
      pretend = true

    else
      unless to
        to = arg
      else
        unless from
          from = Regexp.new arg
        else
          files << arg
        end
      end
  end
end

unless from and to and files.length > 0
  usage
  exit
end




files.each do |file|
  new_name = file.gsub( from, to )
  puts "#{file} -> #{new_name}"
  mv file, new_name unless defined?( pretend )
end