Wait for a file to finish writing before reading.

[unaligned]

I feel like this should be a simple solution, but the code I've created so far to deal with it is ugly. My problem is that I'm running the following command to give me a listing of files on a server using Winscp:

Process p = rt.exec("cmd /c winscp.com <connection> /command ls > ./bin/temp.txt close exit");

Once this file is created, I want to parse it to determine which files from the directory I want to download. The parsing works when the file already exists (but I want the program to delete it every time) or if I give the application a Thread.wait(); call that is long enough for the file to conclude writing. However, if I do not wait, the program executes and fails to download the files because the file is not completely written when it begins to parse.

A third option I'm working with is:

long prevLength = 0;
Thread.sleep(300);
long newlength = file.length();
System.out.println("Previous size: " + prevLength); // print out the size for testing
System.out.println("New size: " + newlength);// print out the size for testing
		
while(prevLength < newlength){
	prevLength = newlength;
	Thread.sleep(250);
	newlength = file.length();
	System.out.println("Previous size: " + prevLength);// print out the size for testing
	System.out.println("New size: " + newlength);// print out the size for testing
}

But again, I don't like this method even if it works because it's ugly and uses arbitrary Thread.wait() calls. How can I cleanly determine when the file is done writing and that it is safe to parse? Ideas?

[doWhile]

Rather than pipe it to a file, you could try to get the InputStream of the process and read this stream...if you wrap the stream in a Reader, the read method will return the appropriate cue to exit a reading loop when the process is complete (for example, using a BufferedReader the readLine should return null). You then will have the output in memory already and a cue when the process is complete.

[unaligned]

Rather than pipe it to a file, you could try to get the InputStream of the process and read this stream...if you wrap the stream in a Reader, the read method will return the appropriate cue to exit a reading loop when the process is complete (for example, using a BufferedReader the readLine should return null). You then will have the output in memory already and a cue when the process is complete.

Thank you for this suggestion... I hadn't considered it. In 3 lines of set-up code I have replaced all the ugliness that my previous code had.

[unaligned]

I wrapped the input (aka: output? why so confusing Java?) from the process in a reader as you suggested and it works just as it did before with very few changes... and much more efficiently I might add. Thanks for the help.

[Tolls]

I wrapped the input (aka: output? why so confusing Java?) from the process in a reader as you suggested and it works just as it did before with very few changes... and much more efficiently I might add. Thanks for the help.

Your Java code is reading it, hence it is input.
It's output from the Process yes, but for your program it is input.