the system calls have consequences and results that you may use for your way of detecting file status. very oversimple example is just try to do something to a file, and look at results. if the file is unused, you will get results; if the file is busy, you will get some sort of exception or system flag.
The most approachable way is to use Procmon from the Sysinternals tools released by Microsoft.
https://learn.microsoft.com/en-us/sysinternals/downloads/pro...
Here's a good, basic video tutorial from Scott Hanselman, explainer extraordinaire:
https://www.youtube.com/watch?v=pjKNx41Ubxw
generally you need a process, or file hook; or you want to monitor API calls of running processes
https://kevgo.dev/posts/fs_capture/
https://github.com/evandowning/windbg-trace
for reference, your goal is to detect operations on files and report file, i.e. build a process monitor that you can trust and have granular control.
https://learn.microsoft.com/en-us/windows/win32/api/fileapi/...
the system calls have consequences and results that you may use for your way of detecting file status. very oversimple example is just try to do something to a file, and look at results. if the file is unused, you will get results; if the file is busy, you will get some sort of exception or system flag.
return value:
https://learn.microsoft.com/en-us/windows/win32/api/fileapi/...
GetLastError:
https://learn.microsoft.com/en-us/windows/win32/api/errhandl...
also for reference :
https://learn.microsoft.com/en-us/windows/win32/api/
sysinternals
specifically procmon will probably be what you want