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std::basic_ios::eof

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< cpp‎ | io‎ | basic ios
Revision as of 21:56, 31 May 2013 by P12bot (Talk | contribs)

bool eof() const;

Returns true if the associated stream has reached end-of-file. Specifically, returns true if eofbit is set in rdstate().

Contents

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 eof() returns true.

In typical usage, input stream processing stops on any error; eof() and fail() are then 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) [edit]