Question

Possible Duplicate:
Testing stream.good() or !stream.eof() reads last line twice

I’m working on an assignment where I am required to read data from a file into a linked list. So far I am able to read the file into the linked list with no problem, however everytime i read from the file into the list, i get one extra entry:

here’s my struct:

struct Video { 
char video_name[1024];      // video name
int ranking;                // Number of viewer hits
char url[1024];             // video URL
YouTubeVideo *next;  // pointer to Video structure
}  *head = NULL;        // EMPTY linked list

here’s my read-in code:

void load()
{
ifstream rankFile ("Ranking.dbm");
struct Video *temp;
if (rankFile.is_open())
{
    string line;
    do {

        temp = (Video*)malloc(sizeof(Video)); //allocate space for node 
        temp->next = head;
        head = temp;
        rankFile.getline(temp->video_name,1024);
        rankFile >> temp->ranking;
        getline(rankFile, line); // need to skip 'ranking's
        // unread new-line
        rankFile.getline(temp->url,1024);


    }while (rankFile.good() );

    rankFile.close();
}

else cout << "Unable to open file"; 

return ;

}

it is reading from a file that looks like this:

spiderman
100
spiderman.com
lucy
30
lucy.com
disney
1200
disney.com

these all read in fine, however it appears that the do-while(rankFile.good()); loop goes through one more iteration giving me an empty node in the linked list. I have already tried using all of my getline() statements as conditions of the while loop and that didnt seem to change anything. Also using rankFile != eof gave me no luck.

Is there a way to be checking the next I/O to make sure its not \n or the end of file?

Answer 1

Change it to while(rankFile.good()) instead of using the do...while syntax. do...while doesn’t evaluate the terminating condition on your last iteration until after the contents of the loop have finished processing. A simple while will evaluate before processing the loop body.