I am writing a program in QT in C++. I am using the library libusb.h.
Below is my code - 

```
libusb_device **devs;
libusb_device_handle *dev_handle;
libusb_context *ctx = NULL;
int r;
ssize_t cnt; 
r = libusb_init(&ctx); 
if(r < 0) {
        cout<<"Init Error "<<r<<endl; //there was an error
        return 1;
    }

```

But when I want to build it, the errors is occur.

> 
> /home/test/main.cpp:12: błąd: undefined reference to `libusb\_init'
> 
> 
> 

This is file.pro

```
QT += core
QT -= gui

TARGET = test
CONFIG += console
CONFIG -= app_bundle

TEMPLATE = app

SOURCES += main.cpp

```

Can someone help me pointing out the mistake in my code above?