boost log #2

我们在init()里初始化我们的logger。logging::core::get()返回这个logger。我们现在设置一个过滤器，让logger只打印info和info级别以上的日志。

void init()
{
    logging::core::get()->set_filter
    (
        logging::trivial::severity >= logging::trivial::info
    );
}

int main(int, char*[])
{
    init();

    BOOST_LOG_TRIVIAL(trace) << "A trace severity message";
    BOOST_LOG_TRIVIAL(debug) << "A debug severity message";
    BOOST_LOG_TRIVIAL(info) << "An informational severity message";
    BOOST_LOG_TRIVIAL(warning) << "A warning severity message";
    BOOST_LOG_TRIVIAL(error) << "An error severity message";
    BOOST_LOG_TRIVIAL(fatal) << "A fatal severity message";

    return 0;
}

 你可以在程序里随时改变过滤等级，这样，我们可以开启一个线程用来侦听你要设置的等级。

#include <iostream>
#include <boost/log/core.hpp>
#include <boost/log/trivial.hpp>
#include <boost/log/expressions.hpp>
namespace logging = boost::log;
using namespace std;
void SetFilter1() {
  logging::core::get()->set_filter(logging::trivial::severity >= logging::trivial::info);
}
void SetFilter2() {
  logging::core::get()->set_filter(logging::trivial::severity >= logging::trivial::debug);
}
int main () {
  cout << "hello, world" << endl;
  SetFilter1();
  BOOST_LOG_TRIVIAL(trace) << "A trace severity message";
  BOOST_LOG_TRIVIAL(debug) << "A debug severity message";
  BOOST_LOG_TRIVIAL(info) << "An informational severity message";
  BOOST_LOG_TRIVIAL(warning) << "A warning severity message";
  BOOST_LOG_TRIVIAL(error) << "An error severity message";
  BOOST_LOG_TRIVIAL(fatal) << "A fatal severity message";
  SetFilter2();
  BOOST_LOG_TRIVIAL(trace) << "A trace severity message";
  BOOST_LOG_TRIVIAL(debug) << "A debug severity message";
  BOOST_LOG_TRIVIAL(info) << "An informational severity message";
  BOOST_LOG_TRIVIAL(warning) << "A warning severity message";
  BOOST_LOG_TRIVIAL(error) << "An error severity message";
  BOOST_LOG_TRIVIAL(fatal) << "A fatal severity message";
}