merge.rb

#!/usr/bin/env ruby
#http://pastebin.com/KSS0zU2F

unless ARGV.count == 1
    abort 'Merges sequentially-named files.'
end

outfile = ARGV.first.sub(/.?\d+\z/, '')

if File.size? outfile
    abort 'The outfile already exists.'
end

pattern = ARGV.first.sub(/\d+\z/, '')
pattern.gsub!(/[\[\]\*\{\}]/, "\\\\\\0")
if digits = ARGV.first[ /\d+\z/ ]
    pattern << '[0-9]' * digits.length
else
    pattern << '.[0-9]*'
end

files = Dir.glob(pattern).sort

if files.count < 2
    abort 'There needs to be at least 2 files.'
end

if files.first[ /\d+\z/ ].to_i != 1
    abort 'The first file in the series is missing.'
end

file_count = files.last[ /\d+\z/ ].to_i

unless files.count == file_count
    abort '%s of %s files are missing.' % [
        file_count-files.count, file_count
    ]
end

unless size = File.size?(files.first)
    abort '"%s" is empty.' % files.first
end

if File.size?(files.first) == File.size?(files.last)
    abort 'One or more files seem to be missing.'
end

files[0..-2].each do |path|
    size == File.size?(path) and next
    abort '"%s" has an incorrect size.' % file
end

File.open outfile, 'w' do |outstream|
    files.each do |path|
        puts 'Merging "%s"' % path
        File.open(path) do |instream|
            IO.copy_stream(instream, outstream)
        end
    end
    outstream.fsync
end

files.each(&File.method(:unlink))