std::basic_ostream< _CharT, _Traits >::sentry(3)

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

SYNOPSIS

#include <ostream>

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

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).

References std::basic_ostream< _CharT, _Traits >::basic_ostream(), 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().

  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 flushes the output stream.

References std::ios_base::badbit, std::uncaught_exception(), and std::ios_base::unitbuf.

Member Function Documentation

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

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).

Author

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