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std::basic_ios::fail(3)        C++ Standard Libary	 std::basic_ios::fail(3)

NAME
     std::basic_ios::fail - std::basic_ios::fail

Synopsis
	bool fail() const;

	Returns true if an error has occurred on the associated stream. Specifi-
     cally,
	returns true if badbit or failbit is set in rdstate().

	See  ios_base::iostate	for  the  list of conditions that set failbit or
     badbit.

Parameters
	(none)

Return value
	true if an error has occurred, false otherwise.

Example
     // Run this code

      #include <cstdlib>
      #include <fstream>
      #include <iostream>

      int main()
      {
	  std::ifstream file("test.txt");
	  if (!file) // operator! is used here
	  {
	      std::cout << "File opening failed\n";
	      return EXIT_FAILURE;
	  }

	  // typical C++ I/O loop uses the return value of the I/O function
	  // as the loop controlling condition, operator bool() is used here
	  for (int n; file >> n;)
	     std::cout << n << ' ';
	  std::cout << '\n';

	  if (file.bad())
	      std::cout << "I/O error while reading\n";
	  else if (file.eof())
	      std::cout << "End of file reached successfully\n";
	  else if (file.fail())
	      std::cout << "Non-integer data encountered\n";
      }

See also
	The following table shows the  value  of  basic_ios  accessors	(good(),
     fail(), etc.)
	for all possible combinations of ios_base::iostate flags:

	     ios_base::iostate flags basic_ios accessors
	     eofbit  failbit  badbit good() fail() bad() eof() operator bool op-
     erator!
	     false     false	  false    true     false    false   false  true
     false
	     false    false	true	 false	  true	   true    false   false
     true
	     false     true	  false    false    true     false  false  false
     true
	     false    true	true	 false	  true	   true    false   false
     true
	     true      false	  false    false    false    false   true   true
     false
	     true     false	true	 false	  true	   true    true    false
     true
	     true      true	  false    false    true     false  true   false
     true
	     true     true	true	 false	  true	   true    true    false
     true

	ferror checks for a file error
	       (function)

http://cppreference.com 	   2024.06.10		 std::basic_ios::fail(3)
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