std::basic_...stream::str(3)

🎀 std::basic_...stream::str(3) 🎀

okay bestie, this is the std::basic_...stream::str(3) page from the C++ Standard Libary manual (yes, that spelling is exactly what the header says, periodt). It's all about std::basic_stringstream::str and how she manages the contents of the underlying string object. No skipping, no cap.

💖 NAME 💖

• std::basic_stringstream::str — std::basic_stringstream::str

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🦋 Synopsis 🦋

okay so here are all the overloads, literally every single one, in order:

(1) (until C++20)
std::basic_string<CharT, Traits, Allocator> str() const;

(1) (since C++20)
std::basic_string<CharT, Traits, Allocator> str() const&;

template< class SAlloc >
std::basic_string<CharT, Traits, SAlloc> str( const SAlloc& a ) const;
(2) (since C++20)

std::basic_string<CharT, Traits, Allocator> str() &&;
(3) (since C++20)

void str( const std::basic_string<CharT, Traits, Allocator>& s );
(4)

template< class SAlloc >
void str( const std::basic_string<CharT, Traits, SAlloc>& s );
(5) (since C++20)

void str( std::basic_string<CharT, Traits, Allocator>&& s );
(6) (since C++20)

template< class StringViewLike >
void str( const StringViewLike& t );
(7) (since C++26)

She manages the contents of the underlying string object. That's the whole vibe. Here's the breakdown:

• 1) Returns a copy of the underlying string. Equivalent to return rdbuf()->str();.
• 2) Returns a copy of the underlying string, using a as allocator. Equivalent to return rdbuf()->str(a);.
• 3) Returns a string move-constructed from the underlying string. Equivalent to return std::move(*rdbuf()).str();.
• 4,5) Replaces the contents of the underlying string. Equivalent to rdbuf()->str(s);.
• 6) Replaces the contents of the underlying string. Equivalent to rdbuf()->str(std::move(s));.
• 7) Replaces the contents of the underlying string. Equivalent to rdbuf()->str(t);. This overload participates in overload resolution only if is_convertible_v<const T&, basic_string_view<charT, traits>> is true.

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🌸 Parameters 🌸

• s — new contents of the underlying string
• t — an object (convertible to std::basic_string_view) to use as the new contents of the underlying string
• a — allocator used to construct the returned string

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✨ Return value ✨

• 1,2) A copy of the underlying string object.
• 3) A string move-constructed from the underlying string object.
• 4-7) (none)

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💀 Notes 💀

bestie, listen: the copy of the underlying string returned by str is a temporary object that will be destructed at the end of the expression, so directly calling c_str() on the result of str() (for example in auto *ptr = out.str().c_str();) results in a dangling pointer. 😭 do not do that.

⭐ Feature-test macro ⭐

• __cpp_lib_sstream_from_string_view — Value 202306L, Std (C++26), Feature Interfacing std::stringstreams with std::string_view, (7).

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🧚 Example 🧚

// Run this code — literally run it, bestie:

#include <iostream>
#include <sstream>

int main()
{
    int n;

    std::istringstream in; // could also use in("1 2")
    in.str("1 2");
    in >> n;
    std::cout << "After reading the first int from \"1 2\", the int is "
              << n << ", str() = \"" << in.str() << "\"\n";

    std::ostringstream out("1 2");
    out << 3;
    std::cout << "After writing the int '3' to output stream \"1 2\""
              << ", str() = \"" << out.str() << "\"\n";

    std::ostringstream ate("1 2", std::ios_base::ate);
    ate << 3;
    std::cout << "After writing the int '3' to append stream \"1 2\""
              << ", str() = \"" << ate.str() << "\"\n";
}

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🌈 Output 🌈

After reading the first int from "1 2", the int is 1, str() = "1 2"
After writing the int '3' to output stream "1 2", str() = "3 2"
After writing the int '3' to append stream "1 2", str() = "1 23"

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🫶 See also 🫶

• rdbuf — returns the underlying raw string device object (public member function)
• str — replaces or obtains a copy of the associated character string (public member function of std::basic_stringbuf<CharT,Traits,Allocator>)

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and that's the whole page, bestie 💅 source/version: http://cppreference.com; date: 2024.06.10; footer page name: std::basic_...stream::str(3). mwah 💋