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cscanffeof

Why the fscanf is used 2 times with: while( !feof(File))

why when using fscanf to acquire data from a file, is used 2 times, once before the "!feof(fin)" and later, as shown in the code below:

fscanf(fin, "%s", letta);
while(!feof(fin)){

    fscanf(fin, "%s", letta);
}

the word read is not the same?

Solution

  • No the word read would not be the same since you read from the file twice, you would get different data each time.

    The condition in the while tests to see if you are at the end of file, in order to do that a read attempt must have been made, which requires the fscanf() before the loop.

    Once you are inside the loop you want to continue reading from the file. Presumably there would be more code inside the loop to process the data you are reading.

    In the code you have posted, if you encountered the end of file with your first read attempt, you wouldn't enter the (while) loop.

    Contrast this with a do-while construct where the test is at the bottom of the loop (ie the read occurs only once, at the "bottom" of the loop). There you will always enter the loop at least once.