basic_ios& copyfmt(const basic_ios& other);
Copies the state of the stream
other into *this. This is done in the following sequence:
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 ios_base::iword and ios_base::pword (but not the iword and pword pointers themselves), the callbacks, and the tied stream.
4) Copies the exception mask from
other to *this as if by calling exceptions(rhs.except())
|other||-||another stream to use as source|
 Return value
The second pass through the callbacks may be used to deep-copy the user-defined objects pointed to by the pointers in ios_base::pword
copyfmt() may be used to save and restore the state of a stream. Boost provides a more fine-grained IO state savers library for the same purpose.
makes the ofstream object "out" behave exactly like std::cout, including formatting, tie() to std::cin, etc.