在FileSystemWatcher检测到更改后读取文本文件的最后更改

Question

Relating to my earlier post: Smartest way to monitor log-files in realtime?
I want a FileSystemWatcher to detect changes of a text file (logfile) and afterwards I want it to show me the latest changes!

They are big files >50bm, and a full scan almost every second is very time-consuming.
I though .last() could help, but this code only returns the last row:

 File.ReadText(@"C:\Filename.txt").Last();

I need some code that can continue reading from the last spot and just determine and returns the changes.

Answer 1

如果您只是在文件末尾附加数据，则可以在内存中保存最后读取字节的位置，并在每次通知文件更新时从该位置读取到文件末尾。

Answer 2

FileSystemWatcher won't exactly do what you want. It sees changes at the directory level. Once the file changes it has no history of it's previous contents. Calling Last() on File.ReadText() also has no concept of the files previous state which is why it just returns the last row.

I think the best approach would be to save the EOF's position then each time the FSW raises a file changed event you would read from previous EOF position to the new EOF then update the variable which stores the EOF's position.