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BSLogger - extremely simple logger for C++

Overview

The idea behind BSlogger is to provide an elementary logging class for C++ projects that don't need any advanced logging features.

BSlogger is:

  • header only
  • single class
  • very low overhead

BSlogger supports:

  • colored output
  • time and snapshot logging
  • several log levels, log level control
  • automatic function info

Example usage

Basically all the features are shown in bslogger_examples.cpp

  LOG_INIT_CERR();

  // Log some stuff. The initial loglevel is
  // INFO and lower (INFO, WARNING, ERROR)
  // so the debug info is not displayed
  log(LOG_DEBUG) << "Some text\n";
  log(LOG_INFO) << "Some text\n";
  log(LOG_WARN) << "Some text\n";
  log(LOG_ERR) << "Some text\n";

  // Change the log level
  log.set_log_level(LOG_DEBUG);

  // Now the debug info is displayed
  log(LOG_DEBUG) << "Some text\n";

  // Everything that has a operator<< method
  // for ostreams can be logged
  float x = 3.1415;

  log(LOG_DEBUG) << "The value of x is " << x
                 << ", the address is " << &x
                 << '\n';

  // You can add time snapshots
  log.add_snapshot("before_sleep");
  std::this_thread::sleep_for(std::chrono::milliseconds(2000));
  
  // Log the time since the last snap added
  log.time_since_last_snap();

  // Log the time since a particular snap was added
  log.time_since_snap("before_sleep");

  // Log the time since the log was initialized
  log.time_since_start();

Output:

[ INFO    ][ 2017-02-08T20:04:47 ][ int main(int, char**) ]: Some text
[ WARNING ][ 2017-02-08T20:04:47 ][ int main(int, char**) ]: Some text
[ ERROR   ][ 2017-02-08T20:04:47 ][ int main(int, char**) ]: Some text
[ DEBUG   ][ 2017-02-08T20:04:47 ][ int main(int, char**) ]: Some text
[ DEBUG   ][ 2017-02-08T20:04:47 ][ int main(int, char**) ]: The value of x is 3.1415, the address is 0x7fff17d6f1d8
[ TIME    ][ 2017-02-08T20:04:47 ][ int main(int, char**) ]: Added snap 'before_sleep'
[ TIME    ][ 2017-02-08T20:04:49 ][ int main(int, char**) ]: 2s since snap 'before_sleep'
[ TIME    ][ 2017-02-08T20:04:49 ][ int main(int, char**) ]: 2s since snap 'before_sleep'
[ TIME    ][ 2017-02-08T20:04:49 ][ int main(int, char**) ]: 2s since instantiation

Advanced usage

The macros LOG_INIT_COUT(), LOG_INIT_CERR() and LOG_INIT_CLOG() are shorthands for logger log(std::cout, __PRETTY_FUNCTION__), logger log(std::cerr, __PRETTY_FUNCTION__) and logger log(std::clog, __PRETTY_FUNCTION__). Any std::ostream can be passed to the logger() constructor. The two constructors are:

  • logger(std::ostream&, std::string) - contructs a BSlogger logging to ostream and presenting the supplied string as the namespace.
  • logger(std::ostream&, unsigned, std::string) - construcs a BSlogger using a non default log-level, otherwise same as above.

The log levels are:

  • LOG_SILENT
  • LOG_ERR
  • LOG_WARN
  • LOG_INFO
  • LOG_TIME
  • LOG_DEBUG

The logger will print all messages with the current level and lower. The default log-level is LOG_TIME, the log-level can be modified using the logger::set_log_level(unsigned) function.

The compiler definition -DBSLOG_NO_COLORS will turn off colored output. If one wants to modify the colors, simply replace the BSLOG_* definitions in the header file.