c语言中fprintf函数，向文件中写入数据

#include <stdio.h>
#include <time.h>

int main(void)
{
    FILE *fp;
    time_t current = time(NULL);
    struct tm *timer = localtime(&current);
    
    if((fp = fopen("a.txt", "w")) == NULL)
        printf("\aFile open failed.\n");
    else
    {
        fprintf(fp, "%d-%d-%d; %d-%d-%d\n", timer -> tm_year + 1900, timer -> tm_mon + 1, timer -> tm_mday,
        timer -> tm_hour, timer -> tm_min, timer -> tm_sec);
        fclose(fp);
    }
    return 0;
}

#include <stdio.h>

int main(void)
{
    FILE *fp;
    int a = 100;
    double b = 30.5;
    char str[] = "abcd";
    
    if((fp = fopen("a.txt", "w")) == NULL)
        printf("\aFile open failed.\n");
    else
    {
        fprintf(fp, "%d + %.2f + %s\n", a, b, str);
        fclose(fp);
    }
    return 0;
}