C++ IOS Library - rdstate

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Description

It is used to check get error state flags. The internal error state flags are automatically set by calls to input/output functions on the stream to signal certain errors.

Declaration

Following is the declaration for ios::rdstate function.

iostate rdstate() const;

Parameters

none

Return Value

An object of type ios_base::iostate that can contain any combination of the following state flag member constants −

iostate value (member constant)	indicates	functions to check state flags
		good()	eof()	fail()	bad()	rdstate()
goodbit	No errors (zero value iostate)	true	false	false	false	goodbit
eofbit	End-of-File reached on input operation	false	true	false	false	eofbit
failbit	Logical error on i/o operation	false	false	true	false	failbit
badbit	Read/writing error on i/o operation	false	false	true	true	badbit

Exceptions

Strong guarantee − if an exception is thrown, there are no changes in the stream.

Data Races

Accesses the stream object.

Concurrent access to the same stream object may cause data races.

Example

In below example is shown for ios::rdstate.

#include <iostream>     
#include <fstream>      

int main () {
   std::ifstream is;
   is.open ("test.txt");
   if ( (is.rdstate() & std::ifstream::failbit ) != 0 )
      std::cerr << "Error opening 'test.txt'\n";
   return 0;
}