Boost Log clears log file

问题:

I've been experimenting with Boost Log libraries for C++. My problem is every time the program starts, log file is cleared. Is there any append option or something?

Here is a part of my code:

BOOST_LOG_INLINE_GLOBAL_LOGGER_DEFAULT(my_logger, src::logger_mt)
src::logger_mt& lg = my_logger::get();

logging::add_file_log
(
    keywords::file_name = "error.log%N",
    keywords::rotation_size = 1 * 1024 * 1024,
    keywords::max_size = 10 * 1024 * 1024,
    keywords::format = "[%TimeStamp%]: %Message%",
    keywords::auto_flush = true
);
logging::add_common_attributes();

BOOST_LOG(lg) << "Danger danger!";

回答1:

Yes.

open_mode The mask that describes the open mode for the file. See std::ios_base::openmode.

From here

So add keywords::open_mode = std::ios_base::app.