std::basic_ios<CharT,Traits>::copyfmt
From cppreference.com
| 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:
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.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 IO state savers library for the same purpose.
Example
makes the 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