For loop doesn`t work when add [^\n] to a scanf_s

Question

This program should ask you to add member (people) to a struct and print them on a file but after the first for loop just stop working and jump over the name part. I just found that thing that allow you to add space to a string, tried it but no success... I tried to remove it and it work without any problem so the [^\n] make something go wrong. What is wrong ?

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

struct Staff {
    char Surname[100];
    char Name[100];
    int age;
    char spec[100];
    int id;
} person;

void write();
void leggi();
void trova();

int main() {
    write();
}

void write() {
    int i = 0;
    int n = 1;
    int r;

    FILE *fp;
    fopen_s(&fp, "index.txt", "w+");
    if (fp == NULL) {
        printf("Failed to open file\n");         
        exit(1);
    }

    fprintf(fp, "%d\n", i);

    for (i = 0; i < n; i++) {
        printf("Surame:\n");
        scanf_s("%[^\n]s", person.Surname, 100);
        fprintf(fp, "%s\t\t", person.Surname);
                                             //loop just get over the name part 
        printf("Name:\n");                   //after the first loop
        scanf_s("%s", person.Name, 100);               
        fprintf(fp, "%s\t", person.Name);

        printf("Age:\n");                  
        scanf_s("%d", &person.age);
        fprintf(fp, "%d\t", person.age);

        printf("Specialization\n");
        scanf_s("%s", person.spec, 100);
        fprintf(fp, "%s\n", person.spec);

        printf("Want to enter another? 1=yes  0=no...\n");
        scanf_s("%d", &r);
        if (r == 1)
            n = n + 1;
    }

    rewind(fp);
    fprintf(fp, "%d\n", i);    

    fclose(fp);
}

Answer 1

Change the call of scanf below for entering strings by inserting a space in the beginning of the format string. For example instead of this call

scanf_s("%[^\n]s", person.Surname, 100);

(where the letter s must be removed from the format string) write

scanf_s(" %[^\n]", person.Surname, ( rsize_t )100);
        ^^^^^^^^

This allows to skip leading white space characters in the input buffer.

Pay attention to that changing the condition or the for loop the was as you are doing

for (i = 0; i < n; i++) {
//...
    if (r == 1)
        n = n + 1;
}

makes the code unclear. Instead of the for loop you could use do-while loop.