How to print an entire istream to standard out and string

Question

How do you print an istream variable to standard out. [EDIT] I am trying to debug a scenario wherein I need to ouput an istream to a log file

Answer 1

Edit: I'm assuming that you want to copy the entire contents of the stream, and not just a single value. If you only want to read a single word, check 1800's answer instead.

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The obvious solution is a while-loop copying a word at a time, but you can do it simpler, as a nice oneliner:

#include 
#include 

...

std::istream i;
std::copy(std::istream_iterator(i), std::istream_iterator(), std::ostream_iterator(std::cout));

The stream_iterators use operator << and >> internally, meaning they'll ignore whitespace. If you want an exact copy, you can use std::istreambuf_iterator and std::ostreambuf_iterator instead. They work on the underlying (unformatted) stream buffers so they won't skip whitespace or convert newlines or anything.

You may also use:

 i >> std::noskipws;

to prevent whitespace from disappearing. Note however, that if your stream is a binary file, some other characters may be clobbered by the >> and << operators.