c - 结构和 malloc 代码得到奇怪的输出

Question

又是我，正在进步...我想感谢所有对我的上一个问题发表评论的人，这非常有帮助。到目前为止我得到了这个编译但是有一些我无法解决的奇怪的错误。

void addRecord(){//carries users input data

numRecs++;//increments numRecs by 1 

struct record library; //this will hold info for user input

printf ("Please enter your first name:\n");
fgets(library.fName, sizeof(library.fName), stdin);
printf ("Please enter your last name:\n");
fgets(library.lName, sizeof(library.lName), stdin);
printf ("Please enter your hometown:\n");
fgets(library.hometown, sizeof(library.hometown), stdin);


printf("You entered %s for your first name.\n", library.fName);
printf("You entered %s for your last name.\n", library.lName);
printf("You entered %s for your hometown.\n", library.hometown);


struct record *myNewRecord;//creates a new struct pointer to store   all the old data and new data


myNewRecord = malloc(numRecs * sizeof(struct record));      //allocates space to fit all old data plus the new struct data
if (myNewRecord == NULL)
{
fprintf(stderr,"Out of memory\n");
}

*myNewRecord = library;

fprintf(stderr, "You made it here!!\n");

这些是我从终端获得的结果。看起来源代码中的语法都是正确的，但问题是它出于某种原因跳过了名字 fgets。此外，当它打印出来时，它会以某种方式执行返回。你们能看出这是怎么回事吗？？？附言当我消除 switch case 并且在 main 中只有 addrecord() 时，它不会执行此操作。

ubuntu@ubuntu:~$ 
ubuntu@ubuntu:~$ gcc lab222.c -o lab222
ubuntu@ubuntu:~$ ./lab222

Please select from the following:
 1. Print all records.
 2. Print number of records.
 3. Print size of database.
 4. Add record.
 5. Delete record.
 6. Print number of accesses to database.
 7. Exit.
Enter a number 1-7:4
Please enter your first name:
Please enter your last name:
Don
Please enter your hometown:
Mega
You entered 
 for your first name.
You entered Don
 for your last name.
You entered Mega
 for your hometown.
You made it here!!

Answer 1

改变:

scanf("%d",&sel);
if (scanf("%d", &sel) == 0) {
    fprintf(stderr, "Error, not a valid input. Must be a number from 1 to 7.\n");
    scanf("%s", &c);
    continue;
}

到:

char reponse[MAX];
fgets(response, sizeof response, stdin);
int result = sscanf(response, "%d", &sel);
if (result != 1) {
    fprintf(stderr, "Error, not a valid input. Must be a number from 1 to 7.\n");
    continue;
}

使用 fgets() 后跟 sscanf() 解决了单独使用 scanf() 时不读取换行符的问题。您还在 if 中再次调用了 scanf()，因此它读取了两次输入。