Seg fault in C program that uses bash command by system() function

Question

Im trying to make program print whole content of folder by asking user for path to folder where the content is and then by using system() function I want program to make .txt file with output of ls path > systemOutput.txt and then print it on screen using ncurses lib. There is my code:

#include<stdlib.h>
#include<stdio.h>
#include<ncurses.h>
#include<string.h>
//#include"DevIL/include/IL/il.h"
int main(){
    //defining variables
    char* userInput;
    char *systemInput;
    FILE *file;
    char c;
    //opening ncurses window
    initscr();
    refresh();
    //asking user for folder path which contain photos
    printw("EXIF file reader\n\n\n\n\n\n");
    printw("Please enter the folder path where the photos are located:\n");
    scanw("%s", userInput);
   
    //running bash to print all files in folder
    strcat(systemInput,"ls ");
    strcat(systemInput,userInput);
    strcat(systemInput," > systemOutput.txt");
    system(systemInput);
    //opening system() output
    file=fopen("systemOutput.txt","r");
   if(file){
        while((c=getc(file))!=EOF){
            printw("%c", c);
        }
    }
    if(getch()=='q'){
        endwin();
    }
}