Thread: EOF not found

Hi, I wrote a simple program based on the file io tutorial. It 's supposed to echo a file but unfortunatel it dosent seam to hit the EOF?

Code:

int main(void){

ifstream in("my_file");

char input;

in.get(input);
while(input != EOF){
cout << input;
in.get(input);
}

in.close();

return 1;
}

Any help is appreciated.

Try replacing EOF with NULL - that always works for me

>where is your open function
Right here:

Code:

ifstream in("my_file");

>the way I showed is preferred
Is it really? What about that annoying problem of how the eof flag is not set until after the loop body has begun execution? A better way would be like so:

Code:

while ( in.good() ) {
  // Work with in
}
// If you feel so inclined to make sure nothing went wrong:
if ( in.fail() ) {
  // Handle the error.
}

-Prelude

>In all the reference and text books I have seen
Books are very often wrong. If it works for you then I won't stop you from using it, just be aware that there are problems with your preference, so teaching it to others while explaining it to be the best option is not the best idea.

>Where is book or reference that uses good or fail with text files?
All I have to go on (that I trust) is the C++ Standard dictating that the eof flag is not set until after you try to read past EOF, and the recommendations of many of the best C++ programmers in the world. Also that thing they call experience, I know that your method has problems because I've seen it happen on a regular basis. I'd be glad to quote the standard later if you like, I don't have it with me at the moment.

-Prelude

Prelude needs no corroboration from me, but

Code:

while (!in.eof())
   {

   }

also tests only for the EOF flag and ignores flags, such as 'badbit' and 'failbit', that may be set during the read. The code she suggests accounts for such a possibility and, therefore, should be considered the "preferred" method.

P.S. For what it's worth, this same information is in an old C++ text of mine. (Don't ask Prelude for the "standard", btw. If she says it's in there, it is.)

-Skipper

... and to add a bit more (I don't think this is already said):

Code:

char input;
while (input != EOF)
...

This will never work properly, as EOF is an int and input is a char which will never be able to be equal to the value of EOF.

Code:

while ( in )
   {

   }

The return value is non-zero as long as the 'read' is valid. If the 'read' becomes invalid, the value returned is zero and the loop is terminated. (Just an additional piece of info here.)

I digress to Prelude's code. Assuming that you want to handle an error appropriately, i.e not let the program simply "crash", you'll want to add some error-handling properties to your code.

P.S. Thanks to both Hammer and ygfperson for their input. Much appreciated...by me, if no one else.

-Skipper