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[英]I use while(scanf(“%[^\n]”, input)!=EOF), but even I haven't entered anything, it goes into infinite loop
[英]I am trying to validate the user input. But if i entered an invalid character the program goes to an infinite loop
我正在尝试验证用户输入。 在输入无效的情况下,我试图要求用户重新插入正确的数字(双精度)值。
程序无法运行,进入无限循环。
你能给我什么建议吗,我该怎么做? 谢谢。!!
int main() {
double t; /* Input from user */
int check;
check = 0;
/* This loop is use to validate the user input. *
* For example: If the user insert a character value "x". *
* i am trying to ask the user to insert a valid numeric value. */
while (check == 0)
{
printf("Insert the value: ");
if (scanf(" %lf", &t) == 1) {
check = 1; /* Everythink okay. No loop needed */
}
else
{
printf("Failed to read double. ");
check = 0; /* loop aganin to read the value */
fflush( stdout );
}
}
return 0;
}
预期结果:$ ./a.out
插入值:X
无法读取双倍。
插入值:5
实际结果 :
$ ./每年
插入值:X
插入值:无法读取双精度。 插入值:无法读取双精度。 (循环)...
如果输入无效字符,程序将进入无限循环...如果输入无效字符,则程序将进入无限循环
OP的代码只是试图重新尝试以不断地转换相同的失败数据。
当scanf(" %lf", &t) == 0
,非数字输入保留在stdin
,需要删除。 @尤金Sh。 。
int conversion_count = 0;
while (conversion_count == 0) {
printf("Insert the value: ");
// Note: lead space not needed. "%lf" itself consumes leading space.
// if (scanf(" %lf", &t) == 1) {
conversion_count = scanf("%lf", &t);
// conversion_count is 1, 0 or EOF
if (conversion_count == 0) {
printf("Failed to read double.\n");
fflush(stdout);
int ch;
// consume and discard characters until the end of the line.
while ( ((ch = getchar()) != '\n') && (ch != EOF)) {
;
}
if (ch == EOF) {
break;
}
}
}
if (conversion_count == 1) {
printf("Read %g\n", t);
} else {
printf("End-of-file or input error\n");
}
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