C++ IOS Library - rdstate

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
`iostate` value (member constant)	indicates	`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;
}

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