NAME¶

std::basic_ios::copyfmt - std::basic_ios::copyfmt

Synopsis¶

basic_ios& copyfmt(const basic_ios& other);

If other refers to the same object as *this, has no effects. Otherwise, copies the
state of the stream other into *this. This is done in the following sequence:

1) Calls every callback registered by register_callback() passing erase_event as
parameter
2) Copies all member objects from other to *this except for rdstate(), the exception
mask, and rdbuf(). In particular, makes copies of the locale, the formatting flags,
the contents of the arrays std::ios_base::iword and std::ios_base::pword (but not
the iword and pword pointers themselves), the callbacks, and the tied stream.
3) Calls every callback registered by register_callback() passing copyfmt_event as
parameter
4) Copies the exception mask from other to *this as if by calling
exceptions(other.exceptions())

Parameters¶

other - another stream to use as source

Return value¶

*this

Notes¶

The second pass through the callbacks may be used to deep-copy the user-defined
objects pointed to by the pointers in std::ios_base::pword

copyfmt() may be used to save and restore the state of a stream. Boost provides a
more fine-grained I/O state savers library for the same purpose.

Example¶

makes the std::ofstream object "out" behave exactly like std::cout, including
formatting, tie() to std::cin, etc.

// Run this code

#include <iostream>
#include <fstream>

int main()
{
std::ofstream out;

out.copyfmt(std::cout); // copy everything except rdstate and rdbuf
out.clear(std::cout.rdstate()); // copy rdstate
out.basic_ios<char>::rdbuf(std::cout.rdbuf()); // share the buffer

out << "Hello, world\n";
}

Output:¶

Hello, world