std::basic_ios<CharT,Traits>::eof
bool eof() const; |
Returns true
if the associated stream has reached end-of-file. Specifically, returns true
if eofbit
is set in rdstate()
.
See ios_base::iostate
for the list of conditions that set eofbit
.
Parameters
(none).
Return value
true
if an end-of-file has occurred, false
otherwise.
Notes
This function only reports the stream state as set by the most recent I/O operation; it does not examine the associated data source. For example, if the most recent I/O was a get()
which returned the last byte of a file, eof()
returns false
. The next get()
fails to read anything and sets the eofbit
. Only then does eof()
return true
.
In typical usage, input stream processing stops on any error. eof()
and fail()
can then be used to distinguish between different error conditions.
Example
#include <iostream> #include <fstream> #include <cstdlib> 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 | 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 |
checks for the end-of-file (function) |
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