#include <stdio.h>
#include <stdlib.h>
#include <conio.h>

struct towar{
    int numer;
    double cena;
    int ilosc;
    char nazwa[30];
};

void babcia(char * p);

int main(){

    char plik[]="magazyn.txt";
    babcia(plik);
    return 0;
}

void babcia(char *p){
    struct towar point;
    struct towar tempPoint;
    int numer,found;
    FILE * handle;
    FILE * tempHandle;

    printf("Numer: ");
    fflush(stdin);
    scanf("%d", &point.numer);

     printf("Cena: ");
    fflush(stdin);
    scanf("lf", &point.cena);

     printf("Ilosc: ");
    fflush(stdin);
    scanf("%d", &point.ilosc);

     printf("Nazwa: ");
    fflush(stdin);
    scanf("%s", point.nazwa);

    numer=point.numer;
    found=point.ilosc;

    if(handle=fopen(p,"r")){
        if(tempHandle=fopen("temp.txt","a+")){
            while(fread(&point, sizeof(struct towar), 1, handle)){
                if(point.numer==numer){
                   point.ilosc+=found;
                   fwrite(&point,sizeof(struct towar),1,tempHandle);
                }
                else
                   fwrite(&point,sizeof(struct towar),1,tempHandle);
            }

        }
    }

    fclose(handle);
    fclose(tempHandle);
    remove(p);
    rename("temp.txt",p);


}