How do you detect that a file you have opened has been moved after opening

Question

As the title states:

• My program opens a file.
• Something comes along and moves that file. Inode should be the same, but name is different.
• Close the file, then delete, but its not there anymore

So how can I detect that it has been moved and delete the correct filename?

Any ideas?

Answer 1

You could use inotify to detect a change to the old name (look for the IN_MOVE_SELF event). But if your real goal is simply to delete the file's name, you can just do that (using unlink(2)) immediately after opening the file. Unix file semantics will allow you to keep using the open file, and the data on disk will not actually be deleted until your handle is closed. And then no one will be able to rename the file.

Answer 2

try to access(2) the file before closing it. If you get ENOENT, the file has been moved. Follow the /proc/self/fd/$open_file_number/ symlink to find the new filename using readlink(2).

Answer 3

fstat the open file, stat the name, and compare the results.

But, in common with any any possible check, it is still racy; the name may change meaning after any check you make but before you act upon it. Time to revisit your requirements.