如何从配置设置提升日志记录严重性级别？

Question

我希望能够从配置指定日志严重性级别：

# my config file 
LogSeverity = info 

我怎样才能做到这一点？目前，我有这样的事情在我main功能：

// logging settings 
boost::log::trivial::severity_level logSeverity; 
boost::program_options::options_description loggingSettings      
    ("Logging settings");              
loggingSettings.add_options()             
("LogSeverity", value<boost::log::trivial::severity_level>(&logSeverity)  
    ->required(),                
     "log level to output"); 

variables_map vm; 
store(parse_config_file(configFilestream, loggingSettings), vm); 
notify(vm); 

boost::log::core::get()->set_filter(           
    boost::log::trivial::severity >= logSeverity); 
BOOST_LOG_TRIVIAL(info) << "severity " << logSeverity; 

这个程序的输出是：

[2015年5月18日09：58：40.783298] [0x000007f017445078] [资讯]严重性跟踪

不过，我设定的严重性info在我的配置（如上），所以为什么它被设置为trace？

Answer 1

工作的完整示例：

default.conf：

# my config file 
LogSeverity = info 

main.cpp中：

#include <string> 
#include <fstream> 

#include <boost/log/trivial.hpp> 
#include <boost/log/expressions.hpp> 
#include <boost/program_options.hpp> 

int main() 
{ 
    // logging settings 
    boost::log::trivial::severity_level logSeverity; 
    boost::program_options::options_description loggingSettings 
    ("Logging settings"); 
    loggingSettings.add_options() 
    ("LogSeverity", boost::program_options::value<boost::log::trivial::severity_level>(&logSeverity) 
    ->required(), 
    "log level to output"); 

    std::ifstream conf_file("./default.conf"); 
    if (!conf_file) 
     return 1; 

    boost::program_options::variables_map variables_map; 
    boost::program_options::store(boost::program_options::parse_config_file(conf_file, loggingSettings), variables_map); 
    boost::program_options::notify(variables_map); 

    boost::log::core::get()->set_filter(
    boost::log::trivial::severity >= logSeverity); 
    BOOST_LOG_TRIVIAL(info) << "severity " << logSeverity; 

    return 0; 
} 

输出：

[2015-05-19 01:22:57.666571] [0xc000027d] [info] severity info 

Answer 2

这个问题似乎已经是你不能直接y分配给来自program_options的boost::log::trivia::severity类型。为了得到这个工作，我存储着的变量在std::string，然后用>>运营商的价值送入severity类型：

// logging settings 
std::string logSeverityString; 
boost::log::trivial::severity_level logSeverity; 
boost::program_options::options_description loggingSettings      
    ("Logging settings");              
loggingSettings.add_options()             
("LogSeverity", value<boost::log::trivial::severity_level>(&logSeverityString)  
    ->required(),                
     "log level to output"); 

variables_map vm; 
store(parse_config_file(configFilestream, loggingSettings), vm); 
notify(vm); 

std::istringstream{logSeverityString} >> logSeverity; 
boost::log::core::get()->set_filter(           
    boost::log::trivial::severity >= logSeverity); 
BOOST_LOG_TRIVIAL(info) << "severity " << logSeverity;