stringfinder_file

#define _CRT_SECURE_NO_WARNINGS
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <malloc.h>
#define S 100

int main()
{
    FILE* in;
    in = fopen("in.txt", "r");
    if (in == NULL)
    {
        puts("Can't open file!");
        return 0;
    }
    int count = 0;
    char p[100];
    printf("Enter the pattern:\n");
    scanf("%s", &p);
    int n;
    while (!feof(in))
    {
        char str[S];
        fgets(str, S, in);
        if (str[strlen(str) - 1] == '\n')
            n = strlen(str) - 1;
        else
            n = strlen(str);
        for (int i = 0; i < n; i++)
        {
            if (str[i] == p[0] && (i == 0 || !((str[i - 1] >= 'a' && str[i - 1] <= 'z') || (str[i - 1] >= 'A' && str[i - 1] <= 'Z') || (str[i - 1] >= '0' && str[i - 1] <= '9'))))
            {
                int len = 1;
                int j = 1;
                int k;
                for (k = i + 1; str[k] == p[j] && k < n; k++)
                {
                    len++;
                    j++;
                }
                if (len == strlen(p) && !((str[k] >= 'a' && str[k] <= 'z') || (str[k] >= 'A' && str[k] <= 'Z') || (str[k] >= '0' && str[k] <= '9')))
                    count++;
            }
        }

    }
    printf("%s _ %d", p, count);
    fclose(in);
    return 0;
}