Sequentially renames files in a directory.

fileseq.rb

#!/usr/bin/env ruby -wKU
# encoding: UTF-8
#
# Sequentially renames *all* files in a directory.
# You'll be prompted for a filename prefix (ex: "image-") and will
# be shown a preview of the new filenames before the rename is performed.
#
# Installation:
#     1) Symlink this script somewhere on your $PATH, ex: `ln -s fileseq.rb /usr/local/bin/fileseq`
#     2) Make it executable: `chmod +x /usr/local/bin/fileseq`
#
# Usage:
#     1) Change to the directory containing the files you want to rename: `cd ~/photos`
#     2) Follow the prompts and enter a prefix for each file: 'vacation-2012-'
#     3) You'll be shown a preview of all the renames (DSC_1234.jpg => vacation-2012-1.jpg, DSC_1235.jpg => vacation-2012-2.jpg, etc)
#     4) Choose 'Y' to perform the rename or 'n' to abort.
#
# IMPORTANT: the files are renamed according to the sequence they appear in initially.
#

puts("You're about to sequentially rename the files in this directory with a common prefix.")
print("Enter the prefix for the new filenames: ")
prefix = gets().chomp

def get_filenames(prefix)
  files = Dir.glob("*.*")
  result = {}
  files.sort_by.each_with_index do |old_filename, index|
    result[old_filename] = "#{prefix}#{index+1}#{File.extname(old_filename).downcase}"
  end
  result
end

filenames = get_filenames(prefix)
longest_name = filenames.keys.sort_by(&:length).last.length + 4

puts "\nHere's what the result will look like:\n\n"
filenames.each do |old_name, new_name|
  puts "#{old_name.rjust(longest_name)} : #{new_name}"
end

print "\nDoes this look correct? [Y/n] "
looks_right = gets().chomp

puts
if looks_right == "Y"
  filenames.each do |old_name, new_name|
    puts "#{old_name.rjust(longest_name)} => #{new_name}"
    File.rename(old_name, new_name) 
  end
  puts "\nFinished renaming #{filenames.length} files."
else
  puts "Rename aborted. Whew!"