std::ostreambuf_iterator::failed

From cppreference.com
bool failed() const;

Returns true if the iterator encountered the end-of-file condition, that is, if an earlier call to std::basic_streambuf::sputc (made by operator=) returned Traits::eof.

Parameters

(none)

Return value

true if this iterator has encountered the end-of-file condition on output, false otherwise.

Exceptions

(none) (until C++11)
noexcept specification:
noexcept
(since C++11)

Example