Is there a tool I can see to see which parts of the file are being modified? I've seen tools that show me which segments of my hard drive are being accessed, but I want something similar for a single file, if something like that exists.
I'm encrypting a file and I want to see if, once a part is written to disk, that part ever changes again. For example, once the first MB of the file is encrypted and saved to disk and the program moves on, is anything in that first MB updated once encryption is done.
As some detailed context, I have a process where I use gpg4win to encrypt a very large file (36GB), and then I have to FTP it to a remote server. Both steps of this process take many hours, but the FTP takes a bit longer. If encryption just keeps extending the file, but the beginning remains unchanged, then I can start the FTP process as soon as the file is just a little ways in. If the header on my encrypted file gets updated at the end, though, I have to wait until that steps is complete before I start the upload.