std::getline() returns

c++ getline
Ferruccio picture Ferruccio · Nov 3, 2008 · Viewed 21.2k times · Source

I have a loop that reads each line in a file using getline():

istream is;
string line;
while (!getline(is, line).eof())
{
    // ...
}

I noticed that calling getline() like this also seems to work:

while (getline(is, line))

What's going on here? getline() returns a stream reference. Is it being converted to a pointer somehow? Is this actually a good practice or should I stick to the first form?

Answer

Charles Anderson picture Charles Anderson · Nov 3, 2008

The istream returned by getline() is having its operator void*() method implicitly called, which returns whether the stream has run into an error. As such it's making more checks than a call to eof().

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