Cory O'Daniel – These are just words Software development, thoughts, and randomness

gem install mime-types

require "rubygems"
require "mime/types"
require "open3"
 
class File
  attr_reader :mime_type, :media_type, :sub_type, :encoding, :extensions
 
  def extensions
    self.mime if @extensions.nil?
    @extensions
  end
 
  def encoding
    self.mime if @encoding.nil?
    @encoding
  end
 
  def sub_type
    self.mime if @sub_type.nil?
    @sub_type
  end
 
  def media_type
    self.mime if @media_type.nil?
    @media_type
  end
 
  def mime_type
    self.mime if @mime_type.nil?
    @mime_type
  end
 
  def mime
    if @mime_type.nil?
      @mime_type = File.sys_file_cmd(File.expand_path(self.path))
 
      unless @mime_type.nil?
        type = MIME::Types[@mime_type].first
 
        @media_type   = type.media_type if type
        @sub_type     = type.sub_type if type
        @encoding     = type.encoding if type
        @extensions   = type.extensions if type
      end
    end
 
    return @mime_type
  end
 
  def File.mime(path)
    File.sys_file_cmd(path)
  end
 
  def correct_extension!    
    File.correct_extension!(self.path)
  end
 
=begin rdoc
  *Name*:: File.correct_extension!
  *Access*:: public, static
  *Description*:: Corrects a files extension
  *Authors*:: Cory ODaniel
  *Last_Edited*:: Wed Feb 13 12:04:11 PST 2008
  ===Parameters
  * Name: file_path
    * Description: Path to file 
    * Datatype: String
    * Default: None
    * Required: True
  ===Returns
  *Description*:: Path to new file or FALSE
  *Datatype*:: String | False
=end
  def File.correct_extension!(file_path)
 
    extensions = MIME::Types[File.mime(file_path)][0].extensions
 
    return false if extensions.nil?
 
    extension = File.extname(file_path) 
    unless extensions.include?(extension)
      directory = File.dirname(file_path)
 
      file_name = File.basename(file_path).split(".")
      file_name.pop if file_name.size > 1 #Remove the bad extension
 
      file_name.push(extensions.first) #just user the first extension in list
      file_name = file_name.join(".")
 
      begin
        new_path = File.join(directory,file_name)
        File.rename(file_path,new_path)
        return new_path
      rescue Exception => e
        return false
      end
    end
  end
 
  private
 
=begin rdoc
  *Name*:: File.sys_file_cmd
  *Access*:: private, static
  *Description*:: Handles call to system "file" command
  *Authors*:: Cory ODaniel
  *Last_Edited*:: Wed Feb 13 12:13:39 PST 2008
  ===Parameters
  * Name: path
    * Description:  file to get mime info for
    * Datatype: String
    * Default: None
    * Required: True
  ===Returns
  *Description*:: Mime information
  *Datatype*:: String | nil
=end  
  def File.sys_file_cmd(path)
    if File.exist? path
      stdin,stdout,stderr = Open3.popen3(%{file --mime -b #{path}})
 
      file_err  = stderr.gets
      file_out  = stdout.gets
 
      if file_err
        raise Exception, "The 'file' command line binary was not found."
      end
 
      if file_err.nil? && (!file_out.nil? && !file_out.empty?)
        return file_out.split(";")[0].strip
      end
    end
 
    return nil
  end
end

# load the file from above however you wanna do it
File.mime("path/to/your/file.html") => "text/html"
@f = File.open("path/to/your/file.html")
@f.mime #=> "text/html"
@f.extensions #=> ['html', 'htm']
@f.media_type #=> "text"
@f.sub_type #=> "html"
 
@wrong_extension = File.open("path/to/image/with/wrong.extension")
@wrong_extension.correct_extension!
 
# Or as a class method
File.correct_extension!("path/to/a/file/with/a/wrong.extension")