fseek on EOF character

Question

I'm currently using fgetc() in loop for reading whole file.

But I need to detect EOF in two iterations of this loop. I know that EOF can't be returned to stream using ungetc().

What about using

fseek(file, -1, SEEK_CUR)

Is it safe and portable to get before EOF using fseek and read it again?

Thanks.

score 1 · Answer 1 · answered Nov 08 '12 at 14:52

1

On most operating systems, EOF is not a physical character that is present in the file. It's simply a virtual "out of band" character that fgetc() is returning to signal that there is no more input.

Why would you ever need to get the EOF again? There is no more data in the file, so what's the point of "backing up" to hit end of file again?

answered Nov 08 '12 at 14:52

unwind

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This loop is inside function (lexical analysis) and I need that loop to detect it independently from previous characters as next token. – user978734 Nov 08 '12 at 14:56

score 1 · Accepted Answer · edited May 23 '17 at 10:24

You can use

fseek(file, 0, SEEK_END)

If you try to read from it, you'll get your second EOF.

EDIT:

Reading the reference more carefully: "Library implementations are allowed to not meaningfully support SEEK_END (therefore, code using it has no real standard portability)."

I guess your solution is the best one in terms of portability.

Just be careful with fseek (as a note because this is not your case I believe): Using fseek to backtrack

fseek on EOF character

2 Answers2