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std::basic_istringstream<CharT,Traits,Allocator>::str

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

Manages the contents of the underlying string object.

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));.

Contents

[edit] Parameters

s - new contents of the underlying string
a - allocator used to construct the returned string

[edit] Return value

1-2) a copy of the underlying string object.
3) a string move-constructed from the underlying string object.
4-6) (none)

[edit] Notes

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.

[edit] Example

#include <sstream>
#include <iostream>
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";
}

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"

[edit] See also

replaces or obtains a copy of the associated character string
(public member function of std::basic_stringbuf<CharT,Traits,Allocator>) [edit]