C++ IOS Library clear

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Description

It is used to set error state flags. The current value of the flags is overwritten: All bits are replaced by those in state; If state is goodbit (which is zero) all error flags are cleared.

In the case that no stream buffer is associated with the stream when this function is called, the badbit flag is automatically set (no matter the value for that bit passed in argument state).

Declaration

Following is the declaration for ios::clear function.

void clear (iostate state = goodbit);

Parameters

state − An object of type ios_base::iostate that can take as value 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

Return Value

none

Exceptions

Basic guarantee − if an exception is thrown, the stream is in a valid state. It throws an exception of member type failure if the resulting error state flag is not goodbit and member exceptions was set throw for that state.

Data Races

Modifies the stream object.

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

Example

In below example explains about ios::clear function.

#include <iostream>
#include <fstream>

int main () {
   char buffer [80];
   std::fstream myfile;

   myfile.open ("test.txt",std::fstream::in);

   myfile << "test";
   if (myfile.fail()) {
      std::cout << "Error writing to test.txt\n";
      myfile.clear();
   }

   myfile.getline (buffer,80);
   std::cout << buffer << " successfully read from file.\n";

   return 0;
}