No logs file getting created

问题

I am using the example at the following link.

https://www.boost.org/doc/libs/1_57_0/libs/log/doc/html/log/detailed/utilities.html#log.detailed.utilities.setup.settings_file

My code is as follows.

#include "stdafx.h"
#include <iostream>
#include <fstream>

#include <boost/log/core.hpp>
#include <boost/log/trivial.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/utility/setup/file.hpp>
#include <boost/log/utility/setup/common_attributes.hpp>
#include <boost/log/utility/setup/from_stream.hpp>
#include <boost/log/utility/setup/settings.hpp>
#include <boost/log/utility/setup/from_settings.hpp>
#include <boost/regex.hpp>

namespace logging = boost::log;
namespace keywords = boost::log::keywords;
#define BOOST_LOG_DYN_LINK 1


int main(int, char*[])
{
    //init_logging();
    std::ifstream file("settings.ini");
    logging::init_from_stream(file);

    BOOST_LOG_TRIVIAL(trace) << "This is a trace severity message";
    BOOST_LOG_TRIVIAL(debug) << "This is a debug severity message";
    BOOST_LOG_TRIVIAL(info) << "This is an informational severity message";
    BOOST_LOG_TRIVIAL(warning) << "This is a warning severity message";
    BOOST_LOG_TRIVIAL(error) << "This is an error severity message";
    BOOST_LOG_TRIVIAL(fatal) << "and this is a fatal severity message";

    return 0;
}

My settings.ini file look as follows.

# Logging core settings section. May be omitted if no parameters specified within it.
[Core]
DisableLogging=false
Filter="%Severity% > 3"

# Sink settings sections
[Sinks.MySink1]

# Sink destination type
Destination=TextFile
FileName="MyApp.log"
RotationSize=1024

# Formatter string. Optional, by default only log record message text is written.
Format="<%TimeStamp%> - %Message%"

# The flag shows whether the sink should be asynchronous
Asynchronous=false

However no file is getting created. What am I doing wrong?

回答1:

Everything works right up until you add the filter:

 Filter="%Severity% > 3"

Googling a bit (via Boost.Log Configuration Files e.g.) I found:

How to configure severity_logger using init_from_settings() to get the custom severity levels in the log?

You have to register any user-defined attribute value types with the library in order to be able to use it with filter and format parsers. This includes your severity level enum.

Add it like:

logging::register_simple_filter_factory<logging::trivial::severity_level>("Severity");

Now, fix the filter expression to use the text representation:

Filter="%Severity% > debug"

In similar vein, you need to add the TimeStamp attribute to core:

logging::core::get()->add_global_attribute("TimeStamp", logging::attributes::local_clock());

Now it all works:

#include <fstream>
#include <iostream>

#include <boost/log/attributes.hpp>
#include <boost/log/core.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/trivial.hpp>
#include <boost/log/utility/setup/common_attributes.hpp>
#include <boost/log/utility/setup/file.hpp>
#include <boost/log/utility/setup/from_settings.hpp>
#include <boost/log/utility/setup/from_stream.hpp>
#include <boost/log/utility/setup/settings.hpp>
#include <boost/regex.hpp>

namespace logging = boost::log;
namespace keywords = boost::log::keywords;
#define BOOST_LOG_DYN_LINK 1

int main(int, char *[]) {
    std::ifstream file("settings.ini");
    logging::core::get()->add_global_attribute("TimeStamp", logging::attributes::local_clock());
    logging::register_simple_filter_factory<logging::trivial::severity_level>("Severity");

    logging::init_from_stream(file);

    BOOST_LOG_TRIVIAL(trace) << "This is a trace severity message";
    BOOST_LOG_TRIVIAL(debug) << "This is a debug severity message";
    BOOST_LOG_TRIVIAL(info) << "This is an informational severity message";
    BOOST_LOG_TRIVIAL(warning) << "This is a warning severity message";
    BOOST_LOG_TRIVIAL(error) << "This is an error severity message";
    BOOST_LOG_TRIVIAL(fatal) << "and this is a fatal severity message";
}

Which writes to MyApp.log:

<2018-09-01 00:36:11.972436> - This is an informational severity message
<2018-09-01 00:36:11.972712> - This is a warning severity message
<2018-09-01 00:36:11.972735> - This is an error severity message
<2018-09-01 00:36:11.972747> - and this is a fatal severity message

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来源：https://stackoverflow.com/questions/52122996/no-logs-file-getting-created