Whats the optimal conditional for counting number of lines in text file?

Question

I've got the following code where I'm trying to count the number of lines in an input file, and I've tried several different ways of implementing it, but no luck.

int checkData(string File)
{
string temp;
int linecount = 0;
ifstream input(File);
input.open(File);

while ()
    {   
        getline(input,temp);
        linecount++;
        temp.clear();
    }
return linecount;

}

So far, I've tried:

while(!input.eof())
    {
     ...
    }

and

while(getline(input,temp).good())
    {
     ...
    }

The first doesnt break the loop, and I'm not quite sure why. (I'm fairly sure) that getline has a built in stream buffer, so it should automatically read the net line everytime I pull in a line and throw it back out, but no dice. For the second, the loop doesn't execute at all, which still doesn't make sense to me (that says that the first line of file isn't good input?). The test file I'm using is:

this is a test     this     Cake
this is a test     this     Cake
this is a test     this     Cake
this is a test     this     Cake

So linecount should be returning as 4 when executing correctly. Before I execute this, I've already checked to make sure the file is opening correctly.

output

The first is well known problem. Removing `.good()` from second should solve it. — Incomputable, Mar 27 '17 at 18:38
Just ran that, and it still doesn't execute the while loop when removing the .good() flag. — Graham Wilson, Mar 27 '17 at 18:40
@GrahamWilson You should double check this -- removing good() should indeed fix your problem (not just in principle; I copied and compiled your code). BTW, temp.clear() isn't necessary. — jwimberley, Mar 27 '17 at 18:42
@GrahamWilson, [wandbox disagrees with you](https://wandbox.org/permlink/IJTOnbW5ES8ING3B). — Incomputable, Mar 27 '17 at 18:43
I'll include a screenshot of the output with the edited code in the original post. — Graham Wilson, Mar 27 '17 at 18:45
See http://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-considered-wrong regarding the first version — Barmar, Mar 27 '17 at 18:48

score 3 · Answer 1 · answered Mar 27 '17 at 18:44

3

int number_of_lines = 0;
string line;
ifstream myfile("textexample.txt");
while (std::getline(myfile, line))
    ++number_of_lines;

Hope it helps.

answered Mar 27 '17 at 18:44

Eklavya

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Whats the optimal conditional for counting number of lines in text file?

1 Answers1