std::basic_ios<CharT,Traits>::operator!
From cppreference.com
bool operator!() const; |
||
Returns true if an error has occurred on the associated stream. Specifically, returns true if badbit
or failbit
is set in rdstate().
Contents |
[edit] Parameters
(none)
[edit] Return value
true if an error has occurred, false otherwise.
[edit] 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"; }
[edit] 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 | operator! |
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 |