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C: Why "while( !feof( file ) )” is always wrong

+3 votes

Lot of material is there on net, but everywhere it is bulky to read, can someone provide crisp and to the point answer.

posted Oct 7, 2014 by anonymous

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one question what is "file" in  < feof(file) >
it is a file name or a file descriptor?

1 Answer

+2 votes
feof(fd) ; 
    where fd is a valid file descriptor of some file having some data in it. 
    fd = fopen(file_name);

As we know that <feof()> will return set value (mostly positive value) if end of file occurs.
As per your statement :

while (!feof(file)) {

There might be two things which is causing it to always fails:
1: Your file reaches the end of file so it return positive value, on which applying ! which converted it to 0 (zero).

2: Or you are passing a file name or an invalid file descriptor as "file" which causing it error, and return -1
and again applying not (!) on -1 it becomes 0 (zero) which again make while() fails.

answer Oct 13, 2014 by Arshad Khan
Thanks Arshad makes sense :)
Thanks for the appreciation.   :)
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