-1

I want to build file sync software. Is there any way to get exact file changes (or at least changes size) with kernel systems like I-notify or others?

EDIT: I'm interested in the following scenario with I-notify: When getting IN_MODIFY event on a file I want retrieve in some way changed lines of the file (some kind of a file diff format). Are there any linux kernel tools to achieve this?

Grigoriy Rozhkov
  • 1
  • 2

2 Answers2

1

Even if there were such a kernel feature, it would not work in practice. You see, most editors modify files by creating a copy, then renaming it over the original one. This way the user is assured of getting either the old contents or the new contents, never a mix between the two.

The only real option is to take snapshots of the file (at e.g. when file is closed when it was open for writing, or when the file is replaced with a new one), and compare the snapshots, to find which part was changed.

Comparing two versions of a file to see which part of it was changed is itself a difficult question, as it definitely depends on the file format. For source code, unified diffs work well, but for other types (including plain text files that are not line-oriented), it's not that simple.

Nominal Animal
  • 38,216
  • 5
  • 59
  • 86
-1

Could you please refine your question? The inotify API on Linux does monitor such changes, and similar changes such as if a file was open, if a file inside a directory (or the directory itself) was moved and file deletions etc.

For more, see here: (http://man7.org/linux/man-pages/man7/inotify.7.html)

EDIT: I believe I misread the question the first time around, if I did, yes such programs exist and the inotify API is the primary one existing within the Linux kernels. See the above link for a comprehensive guide on the different functions it provides.

Michael Shepherd
  • 1
  • 2