The C++ std::ios::copyfmt() function is used to copy the format settings of one stream to another. It transfer settings like flags, precision, and fill character from one stream object to another, ensuring consistent formatting.
By using the copyfmt() we can streamline code and maintain the formatting consistency.
After the call, the following member functions return the same for rhs and *this −
element description flags format flags width field width precision precision getloc selected locale iarray internal extensible array * parray internal extensible array * fill fill character tie tied stream exceptions exceptions mask (last to be copied, see below) SyntaxFollowing is the syntax for std::ios::copyfmt() function.
ios& copyfmt (const ios& rhs);Parameters
This function returns the *this.
ExceptionsIf an exception is thrown, the stream is in a valid state.
Data racesModifies the stream object (*this), and accesses rhs.
Concurrent access to any of the objects may cause data races.
ExampleIn the following example, we are going to consider the basic usage of the copyfmt() function.
#include <iostream> #include <iomanip> int main() { std::cout << "Original Formatting:\n"; std::cout << std::setw(10) << 1122 << '\n'; std::ios x(nullptr); x.copyfmt(std::cout); std::cout << std::fixed << std::setprecision(2); std::cout << "Modified Formatting:\n"; std::cout << 12.12<< '\n'; return 0; }Output
Output of the above code is as follows −
Original Formatting: 1122 Modified Formatting: 12.12Example
Consider the following example, where we are going to transfer formatting between different stream objects.
#include <iostream> #include <iomanip> int main() { std::cout << "Original Formatting :\n"; std::cout << std::hex << 462 << '\n'; std::ostringstream a; std::ostringstream x; x.copyfmt(a); std::cout.copyfmt(a); std::cout << "Modified Formatting :\n"; std::cout << std::dec << 1122 << '\n'; return 0; }Output
Following is the output of the above code −
Original Formatting : 1ce Modified Formatting : 1122
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