std::basic_ostream::sentry

• If any of its internal error flags is set, the function may set its failbit flag and return.
• If it is a tied stream, the function flushes the stream it is tied to (if its output buffer is not empty), unless the function determines that synchronization is not necessary.
  On failure, it may set the failbit flag.
  

• If the unitbuf format flag is set, and there are no uncaught exceptions, the function flushes the stream (as if calling rdbuf()->pubsync()).
  

  If the unitbuf format flag is set, and neither there are uncaught exceptions nor any internal error flag is set, the function flushes the stream (by calling rdbuf()->pubsync()).
  If this call to pubsync returns -1, the badbit is set without propagating an exception (even if member exceptions has this flag set).
  

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class sentry {
public:
  explicit sentry (basic_ostream& os);
  ~sentry();
  operator bool() const;
private:
  sentry (const sentry&);             // not defined
  sentry& operator= (const sentry&);  // not defined
};

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class sentry {
public:
  explicit sentry (basic_ostream& os);
  ~sentry();
  explicit operator bool() const;
  sentry (const sentry&) = delete;
  sentry& operator= (const sentry&) = delete;
};

Members

explicit sentry (basic_ostream& os);

Prepares the output stream for an output operation, performing the actions described above.

~sentry();

Performs the operations described above.

explicit operator bool() const;

When the object is evaluated, it returns a bool value indicating whether the sentry constructor successfully performed all its tasks: If at some point of the construction process, an internal error flags was set, this function always returns false for that object.

See also

basic_ostream::operator<<

Insert formatted output (public member function)