How do I distinguish between an EOF character, and

Question

When reading a file, I understand the last character provided is an EOF. Now, what happens, when I have an EOF character in that file?

How do I distinguish between the "real" end of a file, and the EOF character?

Answer 1

Assuming you're talking about C, EOF is -1, which is not a character (hence there is no confusion).

Answer 2

I decided to move my comments to an answer.

You can't have an "EOF character" in your file because there is no such thing. The underlying filesystem knows how many bytes are in a file; it doesn't rely on the contents of the file to know where the end is.

The C functions you're using return EOF (-1) but that wasn't read from the file. It's just the way the function tells you that you're reached the end. And because -1 isn't a valid character in any character set, there's no confusion.

Answer 3

You need some context for this question. On Windows, there's the outdated DOS concept of a real "EOF character" -- Ctrl-Z. It is actually not possible to tell a "real" one from a "fake" one; a file with an embedded Ctrl-Z will contain some trailing hidden data from the perspective of a program which is actually looking for Ctrl-Z as an end of file character. Don't try to write this kind of code anymore -- it's not necessary.

In the portable C API and on UNIX, a 32-bit -1 is used to indicate end of file, which can't be a valid 8 or 16-bit character, so it's easy to tell the difference.