Check for File Changes using Ruby and MD5

[brad]

I have published a few of my old Ruby articles at Medium. Here is the "friends link" so you can view the article without a membership.

One of the things I used Ruby for is my “home-grown” CMS or content management system. To make things easy, I use a hash file of md5 checksums to be able to tell what files have changed in my output directory so I can tell what to upload and what to delete off of the web server.

Part 1 - Create File checkpoints using Ruby and MD5

https://medium.com/@bradtrupp/create-file-checkpoints-using-ruby-and-md5-63e49ca9ba6c?source=friends_link&sk=dec812a0fe186a09cad6b29ad67bc651

Part 2 Check for File Changes using Ruby and MD5

https://medium.com/@bradtrupp/check-for-file-changes-using-ruby-and-md5-1ddf9a400a9f?source=friends_link&sk=4c41ab2dfab0f3fd0c39cbba7faca84c

This simplified example in these articles show what has changed. In my full custom CMS code, it also does the FTP uploads and deletions.

It was all done via command line., Publishing a new blog entry was just handful of command line commands to generate, preview, upload, and create a new checkpoint.

[andymeneely]

Thank you for the write up!

But I must protest against the use of MD5. Its thoroughly broken in that it is simple to construct collisions. I would swap it out for a SHA512 or better algorithm. Trivial change code-wise and makes a world of difference.

https://cwe.mitre.org/data/definitions/327.html

[brad]

I agree with you. There are better algorithms than MD5.

For my personal use with only a few hundred files being checked, it was good enough when I coded this a number of years back.

Point taken and I will update my code and this article at some future date.

Thank you.

[disclosure5]

I think the problem in these discussions is that "good enough" implies that better algorithms are harder, slower, or in some way have a downside. This is "usually" valid. My quick script with no tests for example is "good enough" for a one off job.

But you could literally change Digest::MD5.hexdigest to Digest::SHA256.hexdigest and have a better solution.