#define _POSIX_C_SOURCE 200809L

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

int replace_line(const char *file_in, const char *file_out, const char *content,
                 int n)
{
    FILE *a = fopen(file_out, "w");
    if (a == NULL)
    {
        return -1;
    }
    FILE *r = fopen(file_in, "r");
    if (r == NULL)
    {
        return -1;
    }

    char *buf = NULL;
    ssize_t e;
    int l = 0;
    size_t count = 0;
    while ((e = getline(&buf, &count, r)) != 0 && e != -1)
    {
        if (l == n)
        {
            if (fputs(content, a) == EOF)
            {
                free(buf);
                return -1;
            }
        }
        else
        {
            if (fputs(buf, a) == EOF)
            {
                free(buf);
                return -1;
            }
        }
        l++;
    }

    fclose(a);
    fclose(r);
    free(buf);

    return 0;
}