Can't read from file all integers of a line (ifstream)

Question

This function is supposed to open a .txt file like this:

1    4    5 

2    4    6

etc. (with tab between numbers)

and save each number in one variable

void Graph::readData(char* fname)
{
    //cout<<"1";
    int x,y,w;//assistant variables
    ifstream input;//stream for reading file
    input.open(fname,ios::in);
    if(!input)
    {
        cerr<<"Input file doesn't exist"<<endl;//error if file doens exist
    }
    else
    {
        cout<<"Input file opened"<<endl;
        cout<<"Reading Data from file..."<<endl;
        while(!input.eof())//till the end of file
        {
            input>>x>>y>>w;//reads the links-site
            cout<<"x: "<<x<<"y:"<<y<<"w: "<<w<<endl;
            insertLink(x,y,w);//inserts them

        }
        input.close();//closing file
    }
}

However, when I "cout" the results I get something like this:

x=1  y=  w=5

x=2  y=  w=6

without y!

Why could this happen?

PS: In addition, eof() becomes true after the file is finished (reads one extra line). How can I stop while iteration properly?

This is the file I'm trying to read from: http://www.speedyshare.com/tpvuD/input.txt

Regarding your PS: [Why is `iostream::eof` inside a loop condition considered wrong?](http://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-considered-wrong) — WhozCraig, Feb 14 '14 at 16:49
Apart from `eof` check, the code should work, which means that the error is in the code you're not showing us or that input file isn't in the format you said it is. — jrok, Feb 14 '14 at 16:56
"...when I 'cout' the results..." those results aren't from the output loop in this posted code. For starters, the posted code has colons (`:`), not equals (`=`). Whatever you're claiming is improper output, it isn't from that loop. My crystal ball tells me the code that *is* writing your output never sends the y-value to the output stream, but without seeing the *real* code, its impossible to say for sure. [That loop works](http://ideone.com/UXZ6I9) once you fix the erroneous while-condition. — WhozCraig, Feb 14 '14 at 16:58
"=" was my... " mistake... http://s12.postimg.org/591imz659/Screenshot_35.png These are the results I get! — syfantid, Feb 14 '14 at 17:03

score 1 · Answer 1 · answered Feb 14 '14 at 16:43

1

To stop the iteration properly, write the loop as:

while(input>>x>>y>>w)//till the end of file
{ /* ... */ }

Do not check input.eof().

answered Feb 14 '14 at 16:43

timrau

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And what if I have something like this: while(!file.eof()) { if(...){ input>>x; } else { input>>x>>y>>w; } } – syfantid Feb 14 '14 at 16:47
Then, `while(input>>x) { if(...) { ... } else { input>>y>>w; ... }` – timrau Feb 14 '14 at 16:51

Can't read from file all integers of a line (ifstream)

1 Answers1