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There is a c++ code for capturing from webcam. This is a code.

#include <iostream>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>

using namespace std;
using namespace cv;

int main(int argc, const char *argv[])
{
    VideoCapture vid(0);
    if(!vid.isOpened()){
        cout<<"Camera could not load..."<<endl;
        return -1;
    }
    namedWindow("webcam",CV_WINDOW_AUTOSIZE);
    while(1){
        Mat frame;
        bool ctrl = vid.read(frame);
        imshow("webcam",frame);
        if(waitKey(0) == 27){
            cout<<"The app is ended..."<<endl;
            break;
        }
    }
    return 0;
}

But when I try to compile it : g++ webcam.cpp -lopencv_core -lopencv_highgui it raises an error

/tmp/ccApncrK.o: In function `main':
webcam.cpp:(.text+0x1a): undefined reference to `cv::VideoCapture::VideoCapture(int)'
webcam.cpp:(.text+0x26): undefined reference to `cv::VideoCapture::isOpened() const'
webcam.cpp:(.text+0xc3): undefined reference to `cv::VideoCapture::read(cv::_OutputArray const&)'
webcam.cpp:(.text+0x195): undefined reference to `cv::VideoCapture::~VideoCapture()'
webcam.cpp:(.text+0x1f7): undefined reference to `cv::VideoCapture::~VideoCapture()'
collect2: error: ld returned 1 exit status

Can you help me, please. PS. (I am using Ubuntu...)