std::basic_string<CharT,Traits,Allocator>::copy

size_type copy( CharT* dest, size_type count, size_type pos = 0 ) const;

constexpr size_type copy( CharT* dest, size_type count, size_type pos = 0 ) const;

Copies a substring [pos, pos + count) to character string pointed to by dest. If the requested substring lasts past the end of the string, or if count == npos, the copied substring is [pos, size()).

The resulting character string is not null-terminated.

Parameters

Return value

Number of characters copied.

Exceptions

std::out_of_range if pos > size().

If an exception is thrown for any reason, this function has no effect (strong exception safety guarantee).

Complexity

Linear in count.

Example

#include <iostream>
#include <string>
 
int main()
{
    std::string foo("WINE");
 
    // brace-initialization initializes all characters to 0,
    // providing a null-terminator
    char bar[4]{};
 
    // do not copy the last char, to guarantee null-termination
    foo.copy(bar, sizeof bar - 1);
 
    std::cout << bar << '\n'; // requires bar to be null-terminated
}

WIN

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also