Different while loops (do while vs infinite while), which is better?

Question

which of these codes is better?

do {
 fread( ... );
 if(!feof(fp)) { ... }
}
while(!feof(fp));

or

while(1){
  fread( ... );
  if(!feof(fp)) { ... }
  else break;
}

Thanks.

You should probably check the output of fread(). And I believe for(;;) is faster as it doesn't have to evaluate anything. — Schoentoon, Dec 28 '13 at 17:10
possible duplicate of ["while( !feof( file ) )" is always wrong](http://stackoverflow.com/questions/5431941/while-feof-file-is-always-wrong) — Jonathan Leffler, Feb 28 '14 at 14:52

score 2 · Accepted Answer · edited Feb 28 '14 at 14:52

2

Neither. You are better off making the eof test part of the loop condition (at the top).

~~You can do this:~~

while (!feof(fp)) {
    fread(...);
}

Since fread returns the number of objects read, you ~~could~~ should also do it this way:

while (fread(...) != 0) {
}

edited Feb 28 '14 at 14:52

Jonathan Leffler

answered Dec 28 '13 at 17:21

Ferruccio

score 1 · Answer 2 · answered Dec 28 '13 at 17:07

1

The while loop is better since the do while do the same operations but it's calling the feof() function twice.

answered Dec 28 '13 at 17:07

rullof

You shouldn't call the function twice as it could be changing! You could declare a variable to store the returned value to check it but the `while` still better – rullof Dec 28 '13 at 17:16

haccks · Answer 3 · 2013-12-28T17:27:05.530

0

which is better?

No one is better than another. The only difference in between these two that first one iterate at least once.

edited Dec 28 '13 at 17:27

answered Dec 28 '13 at 17:22

haccks

3 Answers3