Fgets in C++ repeats last line

Question

I have program like (from link text)

FILE* soubor;
char buffer[100];
soubor = fopen("file","r");
string outp = "";
while (! feof(soubor))
{
        fgets(buffer,100,soubor);
        fputs (buffer , stdout);
}
fclose(soubor);

and file like

A
B
C
D
E

and the output of program is

A
B
C
D
E
E

it repeats last line of file twice. I have this problem in other programs too.

Answer 1

The problem is that for the last line, fgets will fail. However you aren't checking feof until the next loop, so you still call fputs which will print the contents of buffer, i.e. the previous line.

Try this:

FILE* soubor;
char buffer[100];
soubor = fopen("file","r");
string outp = "";
while (true)
{
  fgets(buffer,100,soubor);
  if (feof(soubor))
    break;
  fputs (buffer , stdout);
}
fclose(soubor);

Answer 2

Using feof() as the condition for a loop to read from a file nearly always leads to problems. The standard way would look like this:

while (fgets(buffer, 100, infile))
    fputs(buffer, stdout);