C Primer Plus（第六版）14.18 编程练习 第7题

#include
#include
#include
#define MAXTITL  40
#define MAXAUTL  40
#define MAXBKS   10          
char * s_gets(char * st, int n);
struct book {                   
    char title[MAXTITL];
    char author[MAXAUTL];
    float value;
    int dele;
};

int main(void)
{
    struct book library[MAXBKS]; 
    int count = 0;
    int index, filecount;
    FILE * pbooks;
    int size = sizeof (struct book);
    
    if ((pbooks = fopen("book.dat", "r+b")) == NULL)
    {
        fputs("Can't open book.dat file\n",stderr);
        exit(1);
    }
    rewind(pbooks);
    while (count < MAXBKS && fread(&library[count], size,1, pbooks) == 1)
    {
        if (count == 0)
            puts("Current contents of book.dat:");
        printf("%s by %s: $%.2f\n",library[count].title,
                library[count].author, library[count].value);
        count++;
    }
    filecount = count;
    puts("Enter the line number to edit,0 to quit:");
    while (count <= MAXBKS && scanf("%d",&count) != EOF
           && count!=0)
    {
        while (getchar() != '\n')
            continue;                /* clear input line  */
        printf("Enter 1 to delete,0 to edit.",count);  
        scanf("%d",&library[count-1].dele);
        while (getchar() != '\n')
               continue;
        if(library[count-1].dele!=1) 
        {
        printf("edit row %d title.",count);
        s_gets(library[count-1].title, MAXAUTL);
        printf("edit row %d author.",count);
        s_gets(library[count-1].author, MAXAUTL);
        printf("edit row %d value.",count);
        scanf("%f", &library[count-1].value);
           while (getchar() != '\n')
            continue;     
        }
        puts("input row number to edit,0 to quit:");
    }
    rewind(pbooks);
    if (count == 0)
    {
        puts("Here is the list of your books:");
        for (index = 0; index < filecount; index++)
        {
            if(library[index].dele!=1) //删除的不打印出来 
            {
                printf("%s by %s: $%.2f\n",library[index].title,
                library[index].author, library[index].value);
            }
            fwrite(&library[index], size,1,pbooks);
        }
    }
    puts("Bye.\n");
    fclose(pbooks);
    
    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');   // look for newline
        if (find)                  // if the address is not NULL,
            *find = '\0';          // place a null character there
        else
            while (getchar() != '\n')
                continue;          // dispose of rest of line
    }
    return ret_val;
}