#include <stdio.h>
#include <string.h>
char * s_gets(char * st, int n);
#define MAXTITL   40
#define MAXAUTL   40
#define MAXBKS   100              //最大书籍数

struct book {                     //建立book结构声明
    char title[MAXTITL];
    char author[MAXAUTL];
    float value;
};

int main(void)
{
    struct book library[MAXBKS]; //book 类型结构的数组
    int count = 0;
    int index;
    
    printf("Please enter the book title.\n");
    printf("Press [enter] at the start of a line to stop.\n");
    while (count < MAXBKS && s_gets(library[count].title, MAXTITL) != NULL
           && library[count].title[0] != '\0')

//library[count].title[0] != '\0'判断字符串中的首字符是否为空字符
//按下 Enter 键相当于输入了一个字符串
    {
        printf("Now enter the author.\n");
        s_gets(library[count].author, MAXAUTL);
        printf("Now enter the value.\n");
        scanf("%f", &library[count++].value);
        while (getchar() != '\n')
            continue;          //清理输入行
        if (count < MAXBKS)
            printf("Enter the next title.\n");
    }
    
    if (count > 0)
    {
        printf("Here is the list of your books:\n");
        for (index = 0; index < count; index++)
            printf("%s by %s: $%.2f\n", library[index].title,
                   library[index].author, library[index].value);
    }
    else
    	printf("No books? Too bad.\n");
    
    return 0;
}

char * s_gets(char * st, int n)
{
    char * ret_val;
    char * find;
    
    ret_val = fgets(st, n, stdin);
    if (ret_val)
    {
        find = strchr(st, '\n');   // 查找换行符
        if (find)                  //如果地址不是NULL
            *find = '\0';          // 在此处放置一个空字符
        else
            while (getchar() != '\n')
                continue;          // 处理输入行中剩余的字符
    }
    return ret_val;
}