C++

Reference

<ios>

basic_ios

public member function
<ios> <iostream>

std::basic_ios::operator!

bool operator!() const;
Evaluate stream (not)
Returns true if no error flag is set (either failbit or badbit), and false otherwise.

This is equivalent to calling member fail.

Parameters

none

Return Value

true if either failbit or badbit is set.
false otherwise.

Example

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// evaluating a stream (not)
#include <iostream>     // std::cout
#include <fstream>      // std::ifstream

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

Data races

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

Exception safety

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

See also

basic_ios::fail
Check whether failbit or badbit is set (public member function)
basic_ios::good
Check whether state of stream is good (public member function)