程序运行时学习C scanf函数的问题(编译期间没有错误)C编程绝对初学者指南第8章
程序运行时学习C scanf函数的问题(编译期间没有错误)C编程绝对初学者指南第8章
提问于 2016-07-31 04:26:48
我从书中逐字键入了以下代码：
// Ex program #2 from Ch 8 of ABGTC
// File Ch8Ex2.c
// This is a sample program that asks users for some basic data and prints it on screen in order to show what was entered
#include <stdio.h>
main()
{
float cost;
char topping[24];
int slices;
int month, day, year;
// The first scanf will look for a floating-point variable, the cost of a pizza
// If the user doesn't enter a $ before the cost, it could cause problems
printf("How much does a pizza cost in your area? Enter as $XX.XX\n");
scanf(" $%f", &cost);
// The pizza topping is a string, so your scanf doesn't need an &
printf("What is your favorite one-word pizza topping?\n");
scanf(" %s", topping);
printf("How many slices of %s pizza can you eat in one sitting?", topping);
scanf(" %d", &slices);
printf("What is today\'s date (enter it in XX/XX/XX format).\n");
scanf(" %d/%d/%d", &month, &day, &year);
printf("\n\nWhy not treat yourself to a dinner on %d/%d/%d", month, day, year);
printf("\nand have %d slices of %s pizza!\n", slices, topping);
printf("It will only cost you $%.2f!\n\n\n", cost);
return 0;
}编译时出现零错误(使用Code:Blocks，正如书中推荐和使用的那样)；然而，一旦我运行程序，在输入请求的第一位用户数据(比萨饼的价格，假设我说它将是03.45)后，程序打印出：
"What is your favorite one-word pizza topping?"
"How many slices of 03.45 pizza can you eat in one sitting?"感觉就像是跳过了printf "What is your ...“后面的scanf行。并且不仅提示下面的printf行“多少个切片...”，而且插入03.45作为用户应该在前一行中输入的字符数组/字符串值。
我已经尝试了一些脑海中浮现的不同的调整，但对于我的生活，我无法找出我做错了什么。有什么想法吗？
回答 3
Stack Overflow用户
回答已采纳
发布于 2016-07-31 04:50:54
问题是我在输入回答时没有使用$。在回答第一个问题“一个披萨在你的区域卖多少钱?输入为$XX.XX”时，我的回答是03.45，而由于scanf为$%f，我应该回答$03.45。从"$%f“中去掉$并保持其余部分不变仍然会得到最终打印函数中所需的结果。
希望这对其他使用这本书的人有所帮助！
Stack Overflow用户
发布于 2016-07-31 05:44:02
不检查scanf()的返回值。scanf()返回正确解析和存储的输入数。
在失败的情况下，例如与格式字符串" $%f"的缺失$不匹配，有问题的输入将保留在标准输入中，并将由下一次调用scanf()或任何其他输入函数读取。
您可以使用fgets()读取输入，然后使用sscanf()解析它，直到执行正确的转换或到达文件末尾，从而纠正程序。
请注意，您应该保护格式%s以防止缓冲区溢出:传递要作为scanf(" %23s", topping);读取的最大字符数
下面是一个示例：
#include <stdio.h>
int main(void) {
char line[80];
float cost;
char topping[24];
int slices;
int month, day, year;
for (;;) {
printf("How much does a pizza cost in your area? Enter as $XX.XX\n");
if (!fgets(line, sizeof line, stdin))
return 1;
if (sscanf(line, "$%f", &cost) == 1)
break;
printf("invalid input\n");
}
for (;;) {
printf("What is your favorite one-word pizza topping?\n");
if (!fgets(line, sizeof line, stdin))
return 1;
if (sscanf(line, "%23s", topping) == 1)
break;
printf("invalid input\n");
}
for (;;) {
printf("How many slices of %s pizza can you eat in one sitting?\n", topping);
if (!fgets(line, sizeof line, stdin))
return 1;
if (sscanf(line, "%d", &slices) == 1)
break;
printf("invalid input\n");
}
for (;;) {
printf("What is today\'s date (enter it in XX/XX/XX format).\n");
if (!fgets(line, sizeof line, stdin))
return 1;
if (sscanf(line, "%d/%d/%d", &month, &day, &year) == 3)
break;
printf("invalid input\n");
}
printf("\n\nWhy not treat yourself to a dinner on %d/%d/%d\n",
month, day, year);
printf("and have %d slices of %s pizza!\n", slices, topping);
printf("It will only cost you $%.2f!\n\n\n", cost);
return 0;
}Stack Overflow用户
发布于 2016-07-31 04:37:41
在将浮点变量作为输入后，您缺少对标准输入执行flush操作。
只需使用下面给出的代码，它将解决您的问题。
#include <stdio.h>
main()
{
float cost;
char topping[24];
int slices;
int month, day, year;
printf("How much does a pizza cost in your area? Enter as $XX.XX\n");
scanf(" $%f", &cost);
fflush(stdin); //Just add this line here and your problem is solved.
printf("What is your favorite one-word pizza topping?\n");
scanf(" %s", topping);
printf("How many slices of %s pizza can you eat in one sitting?\n", topping);
scanf(" %d", &slices);
printf("What is today\'s date (enter it in XX/XX/XX format).\n");
scanf("%d/%d/%d", &month, &day, &year);
printf("\n\nWhy not treat yourself to a dinner on %d/%d/%d", month, day, year);
printf("\nand have %d slices of %s pizza!\n", slices, topping);
printf("It will only cost you $%.2f!\n\n\n", cost);
return 0;
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/38678192
复制相关文章
相似问题
腾讯云开发者
