problem while reading a binary file

[shrishjain]

Dear All,

I am having problem in reading bytes from a binary file. I read the
file in following way:

ifstream in("filename");
char c[1];
while(true) {
in.read(&c[0], 1);
if(in.eof()){
cout<<"end of file\n";
break;
}
}

The above code does not read all the file. I find that in.eof() returns
true much before the file really ends. It would be great if someone can
explain me why it is happening this way.

Thanks,
Shrish

 

[Jack Klein]

Dear All,

I am having problem in reading bytes from a binary file. I read the
file in following way:

ifstream in("filename");
char c[1];
while(true) {
in.read(&c[0], 1);
if(in.eof()){
cout<<"end of file\n";
break;
}
}

The above code does not read all the file. I find that in.eof() returns
true much before the file really ends. It would be great if someone can
explain me why it is happening this way.

Thanks,
Shrish

Here are the three most important rules for working with binary files

Rule #1: Open binary files in binary mode.

Rule #2: Don't ever forget rule #1.

Rule #3: Always remember rule #2.

 

[Rolf Magnus]

Dear All,

I am having problem in reading bytes from a binary file. I read the
file in following way:

ifstream in("filename");
char c[1];
while(true) {
in.read(&c[0], 1);
if(in.eof()){
cout<<"end of file\n";
break;
}
}

The above code does not read all the file.

How do you know that? The above code doesn't show you what it read.

 

[zx.zhangxiong]

I tested your code.

It worked fine!

 

[Lionel B]

I tested your code.

It worked fine!

I suspect you didn't test it very well... did you really test it on a *binary* (as opposed to pure text) file? What sort
of binary file? How did you check what had been read?

 

[shrishjain]

Thanks. The three rules really helped. I open it in binary mode and it
really worked.

Shrish

 

[Jack Klein]

Thanks. The three rules really helped. I open it in binary mode and it
really worked.

Shrish

With a little more practice, you will only need to use one of the
rules, instead of all 3!

 

[zx.zhangxiong]

I tested in on both binary and pure text file. Yes, I did not test it
well.
I think it would treate some bytes of binary files as EOF. Otherwise
the test would pass.

  ifstream in("inputfile");
  char c[1];
  int count = 0;
  while(true)
  {
    in.read(&c[0], 1);
    count ++;
    if (in.eof() ) {
      cout << "end of file" << endl; ;
      cout << "count:" << count << endl;
      break;
    }

  }

 

[Lionel B]

I tested in on both binary and pure text file. Yes, I did
not test it well. I think it would treate some bytes of
binary files as EOF.

That's what I was thinking

Otherwise the test would pass.

ifstream in("inputfile");
char c[1];
int count = 0;
while(true)
{
in.read(&c[0], 1);
count ++;
if (in.eof() ) {
cout << "end of file" << endl; ;
cout << "count:" << count << endl;
break;
}

}