versioned_backup

#!/usr/bin/ruby
#
# 1. make a versioned backup of a file

require 'fileutils'    # File.copy
require 'tempfile'

def help_and_exit
  puts "usage: versioned_backup filename [.file_extension]"
  puts
  puts "    makes a versioned backup of filename. If provided"
  puts "    then the version number will be inserted before the"
  puts "    .file_extension"
  puts
  puts "    Example:"
  puts
  puts "    $ ls"
  puts "    foo"
  puts "    $ versioned_backup foo"
  puts "    $ ls"
  puts "    foo"
  puts "    foo.0001"
  puts "    $ versioned_backup foo"
  puts "    $ ls"
  puts "    foo"
  puts "    foo.0001"
  puts "    foo.0002"
  puts "    $ touch bar.mp3"
  puts "    $ versioned_backup bar.mp3 .mp3"
  puts "    $ ls"
  puts "    foo"
  puts "    foo.0001"
  puts "    foo.0002"
  puts "    bar.mp3"
  puts "    bar.0001.mp3"
  exit -1
end

def fatal_error(msg)
  puts "Error: #{msg}"
  exit -1
end

if ARGV[0]
  filename = ARGV[0].chomp
  help_and_exit if filename == "--help"
else
  fatal_error "first argument is missing but required"
  exit -1
end

if ARGV[1]
  file_extension = ARGV[1].chomp
else
  file_extension = nil
end

if not test ?e, filename
  fatal_error "#{filename} doesn't exist"
  exit -1
end

latest_revision = 0

if file_extension != nil
  filename_without_extension = filename.sub(/#{file_extension}$/,'')
else
  filename_without_extension = filename
end

# `ls {filename}.* 2>&1`.each do |name|
Dir.glob("#{filename_without_extension}.*#{file_extension}").each do |name|
  if name =~ /(\d\d\d\d)#{file_extension}$/
    latest_revision = $1.to_i if $1.to_i > latest_revision
  end
end

latest_revision += 1

backup = sprintf( "#{filename_without_extension}.%04d", latest_revision)
if file_extension != nil
  backup += file_extension
end

`cp '#{filename}' '#{backup}'`

exit $?.exitstatus