How to check if a file exists in Ruby on Rails

Posted on 20 July 2006

Sometimes file uploads can go wrong; rather than risk your Rails app falling over, it makes sense to check if the file actually exists.

Your database might point to a filename in your public folder when there's no file there, to allow for this possibility you can do the following:

FileTest.exists?("#{@document.name}")

In the example above the object 'document' has a file_column field 'name'. Calling @document.name returns an absolute path for the upload.

The FileTest needs to be combined with a check to see if you are expecting a file to exist. So in this case it would be:

if @document.name && FileTest.exists?("#{@document.name}")

The reason for this is because you need to check that the filename is actually in the database before checking the file system.

FileTest is a ruby module that allows you to perform various tests on files, it's well worth checking out.

For my rails projects I've been using the file_column plugin to implement file uploads.

View the snippets archive ››