C++ Windows Api Logfile

Monitoring File Handles in Windows: An Introduction

Have you ever found yourself needing to snoop on a log file written by an application, only to realize that the common Windows APIs like CreateFile and OpenFile don’t seem to provide the needed information? This is a common challenge for developers and programmers, especially those who are new to Windows API programming.

In this blog post, we’ll explore a solution to this problem by introducing a tool that simplifies file monitoring in a non-intrusive manner. If you’re trying to check which processes are interacting with a specific file, continue reading.

The Challenge: Why CreateFile and OpenFile Aren’t Enough

When it comes to monitoring file access, many programmers instinctively turn to the CreateFile or OpenFile APIs. However, there can be various reasons these functions may not provide the results you expect:

  • Pre-existing Handles: If the application has already opened the file before you attach your hooks, your queries will return nothing.
  • Other APIs: Applications may utilize different APIs to create or access file handles that are not covered by CreateFile or OpenFile.

A Practical Solution: Using FileMon

Instead of relying on API hooks, which can be complex and intrusive, a more effective approach is to use Sysinternals’ FileMon. Here’s why this might be the solution you’re looking for.

What is FileMon?

FileMon is a system monitoring tool created by Sysinternals that provides real-time file system monitoring. It captures file-related system calls and shows you the details of those calls, including:

  • File names: The exact files that are being accessed.
  • Operation types: Whether the file was created, opened, deleted, etc.
  • Parameters: Additional details regarding the operations being conducted.

You can find FileMon here for more details and to download the tool.

Why Choose FileMon Over API Hooking?

  1. Ease of Use: FileMon is straightforward to set up and use, making it accessible for both seasoned and inexperienced programmers.
  2. Non-Intrusive: Unlike hooks, FileMon operates independently and does not interfere with the normal functioning of applications.
  3. Comprehensive Data: It provides a complete view of file operations, allowing you to gain insights into all interactions with the file system.

Getting Started with FileMon

To start using FileMon, follow these simple steps:

  1. Download FileMon: Visit the Sysinternals website and download the tool.
  2. Launch FileMon: Run the executable. You may need administrative privileges to monitor certain applications.
  3. Filter Results: Use filters to narrow down the view to the file or application you are interested in.
  4. Analyze the Output: Watch the real-time operations being performed and gather the necessary details about file interactions.

Conclusion

In summary, when dealing with file monitoring in Windows, especially if CreateFile or OpenFile does not yield results, consider using Sysinternals’ FileMon. This tool provides a simple, effective, and less intrusive way of monitoring file access and can save you time and effort in your programming tasks.

By leveraging this resource, you can effectively troubleshoot and understand file access patterns in your applications, enabling you to snoop on log files and more without the complexities of API hooking.