user-0 提问: VS中scanf的问题

回复:
user: user-1
content: 都宏定义_CRT_SECURE_NO_WARNINGS了，不用鸟微软的_s函数, 用_s函数的人有多少检查了返回值

user: user-2
content: scanf_s如果是给静态数组输入值就不需要后面的长度，如果是给字符串指针（动态开辟的内存）输入数据就需要后面的长度

user: user-3
content: 查MSDN是Windows程序员必须掌握的技能之一。  Run-Time Library Reference  scanf_s, _scanf_s_l, wscanf_s, _wscanf_s_l  Example  See Also  Send Feedback     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.

user: user-2
content: 引用 4 楼 xxyj6450 的回复:引用 1 楼 ant2012 的回复:scanf_s如果是给静态数组输入值就不需要后面的长度，如果是给字符串指针（动态开辟的内存）输入数据就需要后面的长度另外，不管我输入啥，它读到的都是0，请问它是从哪读到这个值的？  数据是来自控制台呢

user: user-0
content: 引用 1 楼 ant2012 的回复:scanf_s如果是给静态数组输入值就不需要后面的长度，如果是给字符串指针（动态开辟的内存）输入数据就需要后面的长度另外，不管我输入啥，它读到的都是0，请问它是从哪读到这个值的？

user: user-0
content: 引用 1 楼 ant2012 的回复:scanf_s如果是给静态数组输入值就不需要后面的长度，如果是给字符串指针（动态开辟的内存）输入数据就需要后面的长度哥，我的s1是个静态数组呀，怎么也不行。

user: user-3
content: 引用 7 楼 xxyj6450 的回复:[quote=引用 6 楼 zhao4zhong1 的回复:] 查MSDN是Windows程序员必须掌握的技能之一。. 噢，多谢，感谢大神，原来scanf_s输入字符要求带缓冲大小的参数。 但scanf是完全正常的，我传入scanf_s的变量长度是固定的，%s也明确指示了是要输入字符串，这些信息足够判断指针的长度，因此不应再让我输入它的长度。 而且既然是scanf的高级替代，则应在保留scanf特性的基础上再进行高级的控制，而不应带入这种不一致的副作用。 我对这种设计表示不理解。[/quote] 所以很多人包括我在内都 #pragma warning(disable:4996)

user: user-0
content: 引用 6 楼 zhao4zhong1 的回复:查MSDN是Windows程序员必须掌握的技能之一。. 噢，多谢，感谢大神，原来scanf_s输入字符要求带缓冲大小的参数。 但scanf是完全正常的，我传入scanf_s的变量长度是固定的，%s也明确指示了是要输入字符串，这些信息足够判断指针的长度，因此不应再让我输入它的长度。 而且既然是scanf的高级替代，则应在保留scanf特性的基础上再进行高级的控制，而不应带入这种不一致的副作用。 我对这种设计表示不理解。