VS中scanf的有关问题
VS中scanf的问题
不废话，上代码。刚使用VS2013教小舅子写C，从键盘输入一个字符串，复制到另一个字符串数组。书上照抄的，唯一不同的是，把scanf换成了scanf_s,换了以后scanf_s死活读不到键盘输入的内容（如abc)，换成scanf就行，在scanf_s最后加上长度参数也行。按照微软scanf_s的字义，最后一个长度参数是可选的，不应该造成如此大的差别，请大神解释为何scanf_s如此神奇。
------解决思路----------------------
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
------解决思路----------------------
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
------解决思路----------------------
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.
不废话，上代码。刚使用VS2013教小舅子写C，从键盘输入一个字符串，复制到另一个字符串数组。书上照抄的，唯一不同的是，把scanf换成了scanf_s,换了以后scanf_s死活读不到键盘输入的内容（如abc)，换成scanf就行，在scanf_s最后加上长度参数也行。按照微软scanf_s的字义，最后一个长度参数是可选的，不应该造成如此大的差别，请大神解释为何scanf_s如此神奇。
#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
char s1[20], s2[20], *p1 = s1, *p2 = s2;
fflush(stdin);
scanf_s("%s", s1);
//gets_s(s1, 20);
for (; *p1 != 0; p1++, p2++){
*p2 = *p1;
}
*p2 = '\0';
printf("%s\n", s2);
getch();
return 0;
}
------解决思路----------------------
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
------解决思路----------------------
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
------解决思路----------------------
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.