std::basic_ostream::sentry(3)

NAME
std::basic_ostream::sentry - Performs setup work for output streams.

SYNOPSIS

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

Detailed Description

  template<typename _CharT, typename _Traits> 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.' Additional actions may be added by the implementation, and we list them in http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/howto.html#5 under [27.6] notes.

Definition at line 362 of file ostream.

Constructor & Destructor Documentation

  template<typename _CharT, typename _Traits> std::basic_ostream< _CharT, _Traits >::sentry::sentry (basic_ostream< _CharT, _Traits > & __os) [explicit]

The constructor performs preparatory work.Parameters:
    os The output stream to guard.

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').

Definition at line 43 of file ostream.tcc.

  template<typename _CharT, typename _Traits> std::basic_ostream< _CharT, _Traits >::sentry::~sentry () [inline]

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.

Definition at line 390 of file ostream.

References std::ios_base::flags(), std::basic_ios< _CharT, _Traits >::rdbuf(), std::basic_ios< _CharT, _Traits >::setstate(), and std::uncaught_exception().

Member Function Documentation

  template<typename _CharT, typename _Traits> std::basic_ostream< _CharT, _Traits >::sentry::operator bool () [inline]

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).

Definition at line 408 of file ostream.

Author

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