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End of File(EOF)

Dec 1, 2012 at 2:17pm
genclik27 (24)
Hi, I want to use eof() function to stop reading datas from a file when it reaches to end of data. It works well except one case, which is when the file is empty. It takes a random number and make the program crashed. What can I do about that? Am I doing something wrong?

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if( !inputFile.eof( ) )
{
inputFile >> num;
cout << num;
numPrevious = num;
}
Dec 1, 2012 at 4:29pm
AbstractionAnon (6954)
eof() is false, because you haven't attempted to read anything.

The function returns true if the eofbit stream's error flag has been set by a previous i/o operation

http://www.cplusplus.com/reference/ios/ios/eof/
Dec 1, 2012 at 4:42pm
genclik27 (24)
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	ifstream inputFile("compout.txt");
	ofstream outputFile("decompout.txt");


This part reads the file.
inputFile >> num;

Dec 1, 2012 at 7:09pm
genclik27 (24)
Is there anyone who knows solution? Please I need to finish the project.
Dec 1, 2012 at 7:53pm
AbstractionAnon (6954)

This part reads the file.


That is at line 3. The if statement is at line 1.
When you execute the if statement, you haven't yet attempted to read from the file.
Read what I quoted carefully. "flag [is] set by a previous i/o operation". You've performed no previous I/O operation.
Dec 1, 2012 at 8:10pm
Cubbi (4774)
Is there anyone who knows solution?

Don't use the eof() function for something it was never meant to be used:

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if( inputFile >> num )
{
    cout << num;
    numPrevious = num;
}
Dec 1, 2012 at 8:38pm
genclik27 (24)
@AbstractionAnon

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	ifstream inputFile("compout.txt");
	ofstream outputFile("decompout.txt");
	
	int num, numPrevious;
	if( !inputFile.eof( ) )
	{
		inputFile >> num;
		cout << num;
		numPrevious = num;
		outputFile << dictionary[num].key;

	}
	while( !inputFile.eof( ) ) 
	{

		inputFile >> num;
      .
      .
      .
      continues


It is not at line 3, I just wanted to show that I read the line. Do not worry about this part, I know how to read a file. As I said it works very well, but when the file is empty it crashes. What I am asking is when the file is empty.

@Cubbi sorry, I have not shared the code so everybody confused. Here is the real one. I need to use eof somehow. Project says to use it.
Last edited on Dec 1, 2012 at 8:39pm
Dec 1, 2012 at 8:41pm
genclik27 (24)
Program shouldn't enter the inside of if statement. File is empty, I don't get it?
Dec 1, 2012 at 8:52pm
Cubbi (4774)
I need to use eof somehow. Project says to use it.


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    if( inputFile >> num )
    {
        cout << num;
        numPrevious = num;
        outputFile << dictionary[num].key;
    }

    if(inputFile.eof())
    {
        std::cout << "Enf of file reached before reading the first value\n";
        return /* whatever your function returns */;
    }

    while( inputFile >> num )
    {

      .
      .
      .
      continues
    }

    if(inputFile.eof())
    {
        std::cout << "Enf of file reached successfully\n";
    }


Last edited on Dec 1, 2012 at 8:53pm
Dec 1, 2012 at 9:01pm
genclik27 (24)
It is not working again, program does not enter the if statement. There should be something that checks if the file is empty or not? EOF does not do it.
Dec 1, 2012 at 9:03pm
genclik27 (24)
By the way, I said earlier I need to use eof. I used already in while loop, this if statement is for only if the file is empty or not. So, is there any other way, I can use it. Not just eof.
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