Parse android picture filenames to get the creation time and set the mtime of the file

modify_mtime_to_filename.rb

# Parse android picture filenames to get the creation time and set the mtime of the file
# Example: 20180721_230439.jpg's mtime will be set to 2018-07-21 23:04:39 -0400

require 'date'
require "FileUtils"

dir = ARGV[0]

def get_mtime_from_filepath(path)
	filename = File.basename(path, ".*")
	year = filename[0 .. 3].to_i
	month = filename[4 .. 5].to_i
	day = filename[6 .. 7].to_i
	hour = filename[9 .. 10].to_i
	minute = filename[11 .. 12].to_i
	second = filename[13 .. 14].to_i

	return Time.new(year, month, day, hour, minute, second)
end

Dir["#{dir}/**/*"].each { |e| 
	time = get_mtime_from_filepath(e)
	FileUtils.touch e, :mtime => time
	puts "#{File.basename(e)}'s mtime is now #{time}"
}