c++c++17printfstring-view

Correct way to printf() a std::string_view?


I am new to C++17 and to std::string_view. I learned that they are not null terminated and must be handled with care.

Is this the right way to printf() one?

#include<string_view>
#include<cstdio>

int main()
{
    std::string_view sv{"Hallo!"};
    printf("=%*s=\n", static_cast<int>(sv.length()), sv.data());
    return 0;
}

(or use it with any other printf-style function?)


Solution

  • This is strange requirement, but it is possible:

    std::string_view s{"Hallo this is longer then needed!"};
    auto sub = s.substr(0, 5);
    printf("=%.*s=\n", static_cast<int>(sub.length()), sub.data());
    

    https://godbolt.org/z/nbeMWo1G1

    As you can see you were close to solution.