How to know when writing a file has been finished?

Question

I'm writing a program which operates on a file (only reads the file), while another program is writing that file (I've no control over it to use events and I don't know the content of the file). I want a way to know when that program finished writing, to stop my program operating on the file. I used these two method but I don't know which one is reliable and more performance:

1- renaming file to another name, if success, rename it to original name.

2-flush file , if file size has not been changed for a while (e.g 5 sec) then stop operation.

which one is better? is there any better way (more reliable and more performance)?

I'm using windows 7 and qt5.2(or visual studio) for c++.

what do you mean by "operates on file" does it include read and write operation or just read operation? — GingerJack, May 04 '15 at 05:00
you can use IPC for effective communication. Your Writer program sets the event and your reader program will wait on it and when the reader program is triggered ,it should stop reading and close the handle of the file . — GingerJack, May 04 '15 at 05:12
It is operating system specific. Linux has [inotify(7)](http://man7.org/linux/man-pages/man7/inotify.7.html). BTW, the `tail -f` command on POSIX is doing something quite similar... — Basile Starynkevitch, May 04 '15 at 05:30
Is there any string or pattern at the end of the file write. If so, use a Perl script to catch it and then start your program by script — ANjaNA, May 04 '15 at 06:44
no there is no pattern in it, I don't know anything about the content of the file — abdolahS, May 04 '15 at 08:28
Did you checked [this answer?](http://stackoverflow.com/a/20722786/2307070) — Thomas Ayoub, May 04 '15 at 09:20

score 1 · Answer 1 · edited May 17 '15 at 13:08

1

Qt provides a class called QFileSystemWatcher which allows you to monitor files and directories.

edited May 17 '15 at 13:08

Zohar Peled

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answered May 04 '15 at 09:22

GingerJack

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How to know when writing a file has been finished?

1 Answers1