Read into std::string using scanf

Question

As the title said, I'm curious if there is a way to read a C++ string with scanf.

I know that I can read each char and insert it in the deserved string, but I'd want something like:

string a; scanf("%SOMETHING", &a); 

gets() also doesn't work.

Thanks in advance!

Answer 1

this can work

char tmp[101]; scanf("%100s", tmp); string a = tmp; 

Answer 2

There is no situation under which gets() is to be used! It is always wrong to use gets() and it is removed from C11 and being removed from C++14.

scanf() doens't support any C++ classes. However, you can store the result from scanf() into a std::string:

Editor's note: The following code is wrong, as explained in the comments. See the answers by Patato, tom, and Daniel Trugman for correct approaches.

std::string str(100, ' '); if (1 == scanf("%*s", &str[0], str.size())) {     // ... } 

I'm not entirely sure about the way to specify that buffer length in scanf() and in which order the parameters go (there is a chance that the parameters &str[0] and str.size() need to be reversed and I may be missing a . in the format string). Note that the resulting std::string will contain a terminating null character and it won't have changed its size.

Of course, I would just use if (std::cin >> str) { ... } but that's a different question.