sprintf:
http://www.cplusplus.com/reference/clibrary/cstdio/sprintf/
Portotype: int printf(char* str, const char* format, parameters);
Writes into the array pointed by str a C string consisting on a sequence of data formatted as the format argument specifies. After the format parameter, the function expects at least as many additional arguments as specified in format.
This function behaves exactly as printf does, but writing its result to a string instead of stdout. The size of the array passed as str should be enough to contain the entire formatted string .
Return value:
On success, the total number of characters written is returned. This count does not include the additional null-character automatically appended at the end of the string.
//Success
//The size of str is long enough
//the number of additional number match with the format
const int size = 25;
char *str = new char[size];
//same as int flag1 = sprintf(str,"%s is written to str.","Test","tEST");
int flag1 = sprintf(str,"%s is written to str.","Test");
//Console: 23-Test is written to str
cout << flag1 << "-" << str << endl;
//Failure1
//additional arguments numbers is less than specified is format
//the second %s transmited as unrecognizable words
const int size = 25;
char *str = new char[size];
int flag2 = sprintf(str,"%s %s tttttttttttt","Test");
//Console: 19--Test @ tttttttttttt
cout << flag2 << "--" << str << endl;
//Failure2:the size of str is not long enough
// 在dev c++不能運行，vc6.0沒有問題
const int size = 25;
char *str = new char[size];
int flag3 = sprintf(str,"%s jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj","Test");
//VC6.0 Console: Test jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj
//Dev c++: Console: the same as vc6.0 but throws an cannot read memory exception
cout << flag3 << "--" << str << endl;
沒有測試出什么時候出錯返回負值呢！！誰給我一個例子？