Discard/Ignore the rest of a line form a file in c++

Question

I'm looking for a way to read only specific sets of data from a text file. Later I need to "feed" a class with it's content and store the objects in a vector.

My problem is, that I don't need the whole content of the lines and would like to discard or ignore what's coming next and jump to the next line of the text.

I would be very happy if you have a solution or tips for me :)

Each line in the file is structured like this:

brand modelName yearOfProduction price moreStuffIDontCareAbout

Here's what I've come up with so far.

while (inputFile >> brand >> modell >> yearofproduction >> prize) {     
    vecBikes.push_back(Bike(brand, modell, yearofproduction, prize));
    getline(inputFile, puffer);
}

So, what's the problem? What's not working? What errors to you get? — DimChtz, Nov 01 '17 at 18:20
Have you checked a [`std::istream` reference](http://en.cppreference.com/w/cpp/io/basic_istream)? I'm sure you will quickly find a function to *ignore* the remaining line. — Some programmer dude, Nov 01 '17 at 18:22
once you read the line with `getline` you dont need to ignore it anymore because it was already read. not clear what is the problem — 463035818_is_not_an_ai, Nov 01 '17 at 18:25
Possible duplicate of [Read file line by line](https://stackoverflow.com/questions/7868936/read-file-line-by-line) — moooeeeep, Nov 01 '17 at 18:29
It basically works for me but my main intention was, if there's a possibility to do it without reading the whole line, every time. — Kai, Nov 01 '17 at 22:13

Vedant · Answer 1 · 2017-11-01T18:32:22.743

-1

One can solution for this can be by putting delimiter charcter before part to be ignored. And then setting the custom delimiter character, for getline() function Code:

while (getline (inputFile,puffer,(delimiter))
{ 
 }

edited Nov 01 '17 at 18:32

answered Nov 01 '17 at 18:25

Vedant

145
1
13

This way remaining text is still not consumed. – 把友情留在无盐 Mar 21 '19 at 11:39

Felix Glas · Accepted Answer · 2018-10-01T15:20:15.167

Let's say you have a class Bike defined as such.

struct Bike {
    std::string brand, model;
    int year, price;
};

Then I suggest you define an input operator for class Bike.

std::istream& operator>>(std::istream& in, Bike& b) {
    if (std::string line; std::getline(in, line)) {
        std::istringstream line_stream{line};
        line_stream >> b.brand >> b.model >> b.year >> b.price;
    }
    return in;
}

^{(Note the use of the C++17 if-with-initializers syntax).}

Now it is simply a matter of constructing an std::istream_iterator pair for filling your vector from any input stream (let's say the stream is called input here).

std::vector<Bike> vecBikes{std::istream_iterator<Bike>{input},
                        std::istream_iterator<Bike>{}};

Live example

Discard/Ignore the rest of a line form a file in c++

2 Answers2