LinuxQuestions.org - using eof in c++

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twelvenine

10-25-2008 09:20 PM

using eof in c++

i have to write some code that reads from a file until it reaches the end. it looks kind of like this:

Code:

ifstream input;

input.open(inputfile);

while(!input.eof())

{

input >> string;

cout << string << endl;

}

the file that it's reading from looks like this:

Code:

aaa

bbb

ccc

ddd

but for some reason, the above while loop will print out:

Code:

aaa

bbb

ccc

ddd

ddd

i can't figure out what's making it loop the extra time.

twelvenine

10-25-2008 10:21 PM

ok, i did some research and it seems that this is happening because of how the eof flag gets set. apparently it only gets set when you try to do a read, but nothing is there. so, i guess i could change the while loop to:

Code:

input >> string;

while(!input.eof())

{

cout << string;

input >> string;

}

but is there some way that i could update the eof flag without doing a read and throwing off the flow of my reads from the file? like say some function that i could call at the end of the while loop like input.updateeof().

paulsm4

10-25-2008 10:54 PM

Sure -

Code:

#include <stdio.h>

#define BUFLEN 80

...

  char buff[BUFLEN];

  while (fgets (buff, BUFLEN, fp))

    fputs (buff, fp);

  ...

;)

ta0kira

10-25-2008 11:30 PM

Quote:

Originally Posted by twelvenine (Post 3322000)

Code:

while(!input.eof())

It's better to use while (input) so that you also catch error states other than EOF.
ta0kira

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