I cannot run this following code since getting segmentation fault. In the main i enter a string and a substring, whereas in the function i catch the substring and remove it from the string using memmove.

#include <stdio.h>
#include <string.h>

void removeSubstring(char *s, const char *r) {
    int len = strlen(r);
    char *pos;

    while ((pos = strstr(s, r)) != NULL) {
        memmove(pos, pos + len, strlen(pos + len) + 1);
    }
}

int main() {
    char *s;
    const char *r;

    printf("Enter the first string: ");
    scanf(" %[^n]s", &s); 

    printf("Enter the second string: ");
    scanf(" %[^n]s", &r);

    removeSubstring(s, r);

    printf("Modified string: %sn", s);

    return 0;
}

i receive a segmentation fault