std::basic_ostream_sentry - Man Page

sentry (basic_ostream< _CharT, _Traits > &__os)
The constructor performs preparatory work.
~sentry ()
Possibly flushes the stream.
operator bool () const
Quick status checking.

class std::basic_ostream< _CharT, _Traits >::sentry"Performs setup work for output streams.

Objects of this class are created before all of the standard inserters are run. It is responsible for exception-safe prefix and suffix operations.

The constructor performs preparatory work.

Parameters

If the stream state is good (__os.good() is true), then if the stream is tied to another output stream, is.tie()->flush() is called to synchronize the output sequences.

If the stream state is still good, then the sentry state becomes true (okay).

References std::basic_ios< _CharT, _Traits >::bad(), std::ios_base::failbit, std::basic_ios< _CharT, _Traits >::good(), std::basic_ios< _CharT, _Traits >::setstate(), and std::basic_ios< _CharT, _Traits >::tie().

Possibly flushes the stream. If ios_base::unitbuf is set in os.flags(), and std::uncaught_exception() is true, the sentry destructor calls flush() on the output stream.

Quick status checking.

Returns

The sentry state.

For ease of use, sentries may be converted to booleans. The return value is that of the sentry state (true == okay).