为什么有一条scanf_s函数不执行

[学难成]

这是一个判断一个数是否是素数的程序：

#include<stdio.h>

int main()
{int isprime(int);
 int n,flag=1;
 char c;
 while(flag)
{printf("input number:");
 scanf_s("%d",&n);
 
 if(isprime(n))
	 printf("True\n");
 else printf("Flase\n");
 printf("contine or not:");
 scanf_s("%c",&c);
 if(c=='n') flag=0;
}

 return 0;
}

int isprime(int n)
{int i,flag;
 flag=1;
 for(i=2;i<=n/2;i++)
	 if(n%i==0) 
	 {flag=0;break;}
 return(flag);
}

调试结果是：

发现并没有执行第15行的scanf语句，没有提示我输入字符就执行其他语句了。
请问我哪里写错了吗？

[赵4老师]

请判断scanf_s函数的返回值！

[自信男孩]

getchar();
 scanf_s("%c",&c);    //在这句前加一句；用于接收缓存里的回车符

[学难成]

引用 4 楼 cfjtaishan 的回复:

getchar();
 scanf_s("%c",&c);    //在这句前加一句；用于接收缓存里的回车符

把getchar加上后，是可以输入了，可是不管我输入什么，结果都是这个：

[学难成]

引用 3 楼 zhao4zhong1 的回复:

请判断scanf_s函数的返回值！

scanf_s返回值为0，现在可以输入了，可是scanf_s函数还是返回0，求救啊

[赵4老师]

引用 6 楼 u012108273 的回复:

[quote=引用 3 楼 zhao4zhong1 的回复:] 请判断scanf_s函数的返回值！

scanf_s返回值为0，现在可以输入了，可是scanf_s函数还是返回0，求救啊[/quote] Read formatted data from the standard input stream. These are versions of scanf, _scanf_l, wscanf, _wscanf_l with security enhancements as described in Security Enhancements in the CRT. int scanf_s( const char *format [, argument]... ); int _scanf_s_l( const char *format, locale_t locale [, argument]... ); int wscanf_s( const wchar_t *format [, argument]... ); int _wscanf_s_l( const wchar_t *format, locale_t locale [, argument]... ); Parameters format Format control string. argument Optional arguments. locale The locale to use. Return Value Returns the number of fields successfully converted and assigned; the return value does not include fields that were read but not assigned. A return value of 0 indicates that no fields were assigned. The return value is EOF for an error or if the end-of-file character or the end-of-string character is encountered in the first attempt to read a character. If format is a NULL pointer, the invalid parameter handler is invoked, as described in Parameter Validation. If execution is allowed to continue, scanf_s and wscanf_s return EOF and set errno to EINVAL. For information on these and other error codes, see _doserrno, errno, _sys_errlist, and _sys_nerr. Remarks The scanf_s function reads data from the standard input stream stdin and writes the data into the location given by argument. Each argument must be a pointer to a variable of a type that corresponds to a type specifier in format. If copying takes place between strings that overlap, the behavior is undefined. wscanf_s is a wide-character version of scanf_s; the format argument to wscanf_s is a wide-character string. wscanf_s and scanf_s behave identically identically if the stream is opened in ANSI mode. scanf_s doesn't currently support input from a UNICODE stream. The versions of these functions with the _l suffix are identical except that they use the locale parameter passed in instead of the current thread locale. Unlike scanf and wscanf, scanf_s and wscanf_s require the buffer size to be specified for all input parameters of type c, C, s, S, or [. The buffer size is passed as an additional parameter immediately following the pointer to the buffer or variable. For example, if reading a string, the buffer size for that string is passed as follows: char s[10]; scanf("%9s", s, 10); The buffer size includes the terminating null. A width specification field may be used to ensure that the token read in will fit into the buffer. If no width specification field is used, and the token read is too big to fit in the buffer, nothing will be written to that buffer. Note: The size parameter is of type unsigned, not size_t. In the case of characters, one may read a single character as follows: char c; scanf("%c", &c, 1); When reading multiple characters for non-null terminated strings, integers are used as the width specification and the buffer size. char c[4]; scanf("%4c", &c, 4); // not null terminated For more information, see scanf Width Specification. TCHAR.H routine _UNICODE & _MBCS not defined _MBCS defined _UNICODE defined _tscanf_s scanf_s scanf_s wscanf_s _tscanf_s_l _scanf_s_l _scanf_s_l _wscanf_s_l For more information, see Format Specification Fields — scanf functions and wscanf Functions. Requirements Routine Required header scanf_s, _scanf_s_l <stdio.h> wscanf_s, _wscanf_s_l <stdio.h> or <wchar.h> For additional compatibility information, see Compatibility in the Introduction. Example Copy Code // crt_scanf_s.c // This program uses the scanf_s and wscanf_s functions // to read formatted input. #include <stdio.h> int main( void ) { int i, result; float fp; char c, s[81]; wchar_t wc, ws[81]; result = scanf_s( "%d %f %c %C %s %S", &i, &fp, &c, 1, &wc, 1, s, 80, ws, 80 ); printf( "The number of fields input is %d\n", result ); printf( "The contents are: %d %f %c %C %s %S\n", i, fp, c, wc, s, ws); result = wscanf_s( L"%d %f %hc %lc %S %ls", &i, &fp, &c, 2, &wc, 1, s, 80, ws, 80 ); wprintf( L"The number of fields input is %d\n", result ); wprintf( L"The contents are: %d %f %C %c %hs %s\n", i, fp, c, wc, s, ws); } Copy Code 71 98.6 h z Byte characters 36 92.3 y n Wide characters Copy Code The number of fields input is 6 The contents are: 71 98.599998 h z Byte characters The number of fields input is 6 The contents are: 36 92.300003 y n Wide characters .NET Framework Equivalent System::Console::Read System::Console::ReadLine See also Parse methods, such as System::Double::Parse. See Also Concepts Floating-Point Support Stream I/O Locale fscanf, _fscanf_l, fwscanf, _fwscanf_l printf, _printf_l, wprintf, _wprintf_l sprintf, _sprintf_l, swprintf, _swprintf_l, __swprintf_l sscanf, _sscanf_l, swscanf, _swscanf_l Send feedback on this topic to Microsoft.

[学难成]

7楼的，谢谢了，可是看不懂，你能简单点说吗？还是你也不知道？

[赵4老师]

Return Value Returns the number of fields successfully converted and assigned; the return value does not include fields that were read but not assigned. A return value of 0 indicates that no fields were assigned. The return value is EOF for an error or if the end-of-file character or the end-of-string character is encountered in the first attempt to read a character. If format is a NULL pointer, the invalid parameter handler is invoked, as described in Parameter Validation. If execution is allowed to continue, scanf_s and wscanf_s return EOF and set errno to EINVAL.

[赵4老师]

#include <stdio.h>
char s[]="123 ab 4";
char *p;
int v,n,k;
void main() {
    p=s;
    while (1) {
        k=sscanf(p,"%d%n",&v,&n);
        printf("k,v,n=%d,%d,%d\n",k,v,n);
        if (1==k) {
            p+=n;
        } else if (0==k) {
            printf("skip char[%c]\n",p[0]);
            p++;
        } else {//EOF==k
            break;
        }
    }
    printf("End.\n");
}
//k,v,n=1,123,3
//k,v,n=0,123,3
//skip char[ ]
//k,v,n=0,123,3
//skip char[a]
//k,v,n=0,123,3
//skip char[b]
//k,v,n=1,4,2
//k,v,n=-1,4,2
//End.

[AnYidan]

试试scanf_s(" %c",&c);

[zybjtu]

#include<stdio.h>

int main()
{
    int isprime(int);
    int n,flag=1;
    char c;
    while(flag)
    {
        printf("input number:");
        while(1 != scanf_s("%d",&n) )   //判断取到多少，一种比较良好的习惯
            continue;
        if(isprime(n))
            printf("True\n");
        else printf("Flase\n");
        printf("contine or not:\n");
        while(getchar() == '\n');       //因为scanf的时候你输入了'\n'，所以这里是把缓冲里面的'\n'取出。其实你的程序加了这个就好了
        while( 1 != scanf_s("%c",&c) )
            continue;
        if(c=='n') flag=0;
    }

    return 0;
}

int isprime(int n)
{
    int i,flag;
    flag=1;
    for(i=2; i<=n/2; i++)
        if(n%i==0)
        {
            flag=0;
            break;
        }
    return(flag);
}

[max_min_]

可能是取了你上一次输入的回车符了的！

[bedynamic]

这代码写的。。一点都不想看。。。。。。