#include "spdlog/spdlog.h" int main() { spdlog::info("Welcome to spdlog!"); spdlog::error("Some error message with arg: {}", 1); spdlog::warn("Easy padding in numbers like {:08d}", 12); spdlog::critical("Support for int: {0:d}; hex: {0:x}; oct: {0:o}; bin: {0:b}", 42); spdlog::info("Support for floats {:03.2f}", 1.23456); spdlog::info("Positional args are {1} {0}..", "too", "supported"); spdlog::info("{:<30}", "left aligned"); spdlog::set_level(spdlog::level::debug); // Set global log level to debug spdlog::debug("This message should be displayed.."); // change log pattern spdlog::set_pattern("[%H:%M:%S %z] [%n] [%^---%L---%$] [thread %t] %v"); // Compile time log levels // define SPDLOG_ACTIVE_LEVEL to desired level SPDLOG_TRACE("Some trace message with param {}", 42); SPDLOG_DEBUG("Some debug message"); } 

#include "spdlog/spdlog.h" #include "spdlog/sinks/stdout_color_sinks.h" void stdout_example() { // create color multi threaded logger auto console = spdlog::stdout_color_mt("console"); auto err_logger = spdlog::stderr_color_mt("stderr"); spdlog::get("console")->info("loggers can be retrieved from a global registry using the spdlog::get(logger_name)"); }

#include "spdlog/sinks/basic_file_sink.h" void basic_logfile_example() { try { auto logger = spdlog::basic_logger_mt("basic_logger", "logs/basic-log.txt"); } catch (const spdlog::spdlog_ex &ex) { std::cout << "Log init failed: " << ex.what() << std::endl; } }

#include "spdlog/sinks/rotating_file_sink.h" void rotating_example() { // Create a file rotating logger with 5mb size max and 3 rotated files auto max_size = 1048576 * 5; auto max_files = 3; auto logger = spdlog::rotating_logger_mt("some_logger_name", "logs/rotating.txt", max_size, max_files); }

#include "spdlog/sinks/daily_file_sink.h" void daily_example() { // Create a daily logger - a new file is created every day on 2:30am auto logger = spdlog::daily_logger_mt("daily_logger", "logs/daily.txt", 2, 30); } 

// Loggers can store in a ring buffer all messages (including debug/trace) and display later on demand. // When needed, call dump_backtrace() to see them spdlog::enable_backtrace(32); // Store the latest 32 messages in a buffer. Older messages will be dropped. // or my_logger->enable_backtrace(32).. for(int i = 0; i < 100; i++) { spdlog::debug("Backtrace message {}", i); // not logged yet.. } // e.g. if some error happened: spdlog::dump_backtrace(); // log them now! show the last 32 messages // or my_logger->dump_backtrace(32)..

// periodically flush all *registered* loggers every 3 seconds: // warning: only use if all your loggers are thread safe ("_mt" loggers) spdlog::flush_every(std::chrono::seconds(3)); 

// Stopwatch support for spdlog #include "spdlog/stopwatch.h" void stopwatch_example() { spdlog::stopwatch sw; spdlog::debug("Elapsed {}", sw); spdlog::debug("Elapsed {:.3}", sw); } 

// many types of std::container<char> types can be used. // ranges are supported too. // format flags: // {:X} - print in uppercase. // {:s} - don't separate each byte with space. // {:p} - don't print the position on each line start. // {:n} - don't split the output to lines. #include "spdlog/fmt/bin_to_hex.h" void binary_example() { auto console = spdlog::get("console"); std::array<char, 80> buf; console->info("Binary example: {}", spdlog::to_hex(buf)); console->info("Another binary example:{:n}", spdlog::to_hex(std::begin(buf), std::begin(buf) + 10)); // more examples: // logger->info("uppercase: {:X}", spdlog::to_hex(buf)); // logger->info("uppercase, no delimiters: {:Xs}", spdlog::to_hex(buf)); // logger->info("uppercase, no delimiters, no position info: {:Xsp}", spdlog::to_hex(buf)); } 

// create logger with 2 targets with different log levels and formats. // the console will show only warnings or errors, while the file will log all. void multi_sink_example() { auto console_sink = std::make_shared<spdlog::sinks::stdout_color_sink_mt>(); console_sink->set_level(spdlog::level::warn); console_sink->set_pattern("[multi_sink_example] [%^%l%$] %v"); auto file_sink = std::make_shared<spdlog::sinks::basic_file_sink_mt>("logs/multisink.txt", true); file_sink->set_level(spdlog::level::trace); spdlog::logger logger("multi_sink", {console_sink, file_sink}); logger.set_level(spdlog::level::debug); logger.warn("this should appear in both console and file"); logger.info("this message should not appear in the console, only in the file"); }

#include "spdlog/async.h" #include "spdlog/sinks/basic_file_sink.h" void async_example() { // default thread pool settings can be modified *before* creating the async logger: // spdlog::init_thread_pool(8192, 1); // queue with 8k items and 1 backing thread. auto async_file = spdlog::basic_logger_mt<spdlog::async_factory>("async_file_logger", "logs/async_log.txt"); // alternatively: // auto async_file = spdlog::create_async<spdlog::sinks::basic_file_sink_mt>("async_file_logger", "logs/async_log.txt");  } 

#include "spdlog/sinks/stdout_color_sinks.h" #include "spdlog/sinks/rotating_file_sink.h" void multi_sink_example2() { spdlog::init_thread_pool(8192, 1); auto stdout_sink = std::make_shared<spdlog::sinks::stdout_color_sink_mt >(); auto rotating_sink = std::make_shared<spdlog::sinks::rotating_file_sink_mt>("mylog.txt", 1024*1024*10, 3); std::vector<spdlog::sink_ptr> sinks {stdout_sink, rotating_sink}; auto logger = std::make_shared<spdlog::async_logger>("loggername", sinks.begin(), sinks.end(), spdlog::thread_pool(), spdlog::async_overflow_policy::block); spdlog::register_logger(logger); }

// user defined types logging by implementing operator<< #include "spdlog/fmt/ostr.h" // must be included struct my_type { int i; template<typename OStream> friend OStream &operator<<(OStream &os, const my_type &c) { return os << "[my_type i=" << c.i << "]"; } }; void user_defined_example() { spdlog::get("console")->info("user defined type: {}", my_type{14}); } 

// Log patterns can contain custom flags. // the following example will add new flag '%*' - which will be bound to a <my_formatter_flag> instance. #include "spdlog/pattern_formatter.h" class my_formatter_flag : public spdlog::custom_flag_formatter { public: void format(const spdlog::details::log_msg &, const std::tm &, spdlog::memory_buf_t &dest) override { std::string some_txt = "custom-flag"; dest.append(some_txt.data(), some_txt.data() + some_txt.size()); } std::unique_ptr<custom_flag_formatter> clone() const override { return spdlog::details::make_unique<my_formatter_flag>(); } }; void custom_flags_example() { auto formatter = std::make_unique<spdlog::pattern_formatter>(); formatter->add_flag<my_formatter_flag>('*').set_pattern("[%n] [%*] [%^%l%$] %v"); spdlog::set_formatter(std::move(formatter)); } 

void err_handler_example() { // can be set globally or per logger(logger->set_error_handler(..)) spdlog::set_error_handler([](const std::string &msg) { spdlog::get("console")->error("*** LOGGER ERROR ***: {}", msg); }); spdlog::get("console")->info("some invalid message to trigger an error {}{}{}{}", 3); } 

#include "spdlog/sinks/syslog_sink.h" void syslog_example() { std::string ident = "spdlog-example"; auto syslog_logger = spdlog::syslog_logger_mt("syslog", ident, LOG_PID); syslog_logger->warn("This is warning that will end up in syslog."); }

#include "spdlog/sinks/android_sink.h" void android_example() { std::string tag = "spdlog-android"; auto android_logger = spdlog::android_logger_mt("android", tag); android_logger->critical("Use \"adb shell logcat\" to view this message."); }

#include "spdlog/cfg/env.h" int main (int argc, char *argv[]) { spdlog::cfg::load_env_levels(); // or from command line: // ./example SPDLOG_LEVEL=info,mylogger=trace // #include "spdlog/cfg/argv.h" // for loading levels from argv // spdlog::cfg::load_argv_levels(argc, argv); }