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What is std::string and how does it differ from a C-string? How do you convert between std::string and numbers? What common operations does std::string provide? What are the dangers of std::string_view? How does std::string manage memory and what is SSO? How do you efficiently build up a large string? Why should you avoid returning std::string_view to local data? What is the difference between passing const std::string& and std::string_view? What is std::format (C++20) and how does it improve string formatting? How do you handle Unicode and encodings in C++ strings?
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What is std::string_view and why was it added?

Beginner

Answer

std::string_view (C++17) is a non-owning, read-only view over a contiguous sequence of characters (a pointer plus length). It avoids copying when you only need to read a string, and can refer to std::string, C-strings, or substrings uniformly. It's ideal for function parameters that just inspect text.
void log(std::string_view msg);   // no copy for any string type
log("literal"); log(myString);
Real-world example Changing a parameter from const std::string& to string_view lets callers pass literals without constructing a string.

Common follow-ups: Does string_view own its data? | Why use it for parameters?

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All 11 Strings & string_view questions