example.cpp

Go to the documentation of this file.

//
// Copyright(c) 2015 Gabi Melman.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)
 
// spdlog usage example
 
#include <cstdio>
 
void load_levels_example();
void stdout_logger_example();
void basic_example();
void rotating_example();
void daily_example();
void async_example();
void binary_example();
void stopwatch_example();
void trace_example();
void multi_sink_example();
void user_defined_example();
void err_handler_example();
void syslog_example();
void custom_flags_example();
 
#include "spdlog/spdlog.h"
#include "spdlog/cfg/env.h"  // support for loading levels from the environment variable
#include "spdlog/fmt/ostr.h" // support for user defined types
 
int main(int, char *[])
{
    // Log levels can be loaded from argv/env using "SPDLOG_LEVEL"
    load_levels_example();
 
    spdlog::info("Welcome to spdlog version {}.{}.{}  !", SPDLOG_VER_MAJOR, SPDLOG_VER_MINOR, SPDLOG_VER_PATCH);
 
    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("{:>8} aligned, {:<8} aligned", "right", "left");
 
    // Runtime log levels
    spdlog::set_level(spdlog::level::info); // Set global log level to info
    spdlog::debug("This message should not be displayed!");
    spdlog::set_level(spdlog::level::trace); // Set specific logger's log level
    spdlog::debug("This message should be displayed..");
 
    // Customize msg format for all loggers
    spdlog::set_pattern("[%H:%M:%S %z] [%^%L%$] [thread %t] %v");
    spdlog::info("This an info message with custom format");
    spdlog::set_pattern("%+"); // back to default format
    spdlog::set_level(spdlog::level::info);
 
    // Backtrace support
    // Loggers can store in a ring buffer all messages (including debug/trace) for later inspection.
    // When needed, call dump_backtrace() to see what happened:
    spdlog::enable_backtrace(10); // create ring buffer with capacity of 10  messages
    for (int i = 0; i < 100; i++)
    {
        spdlog::debug("Backtrace message {}", i); // not logged..
    }
    // e.g. if some error happened:
    spdlog::dump_backtrace(); // log them now!
 
    try
    {
        stdout_logger_example();
        basic_example();
        rotating_example();
        daily_example();
        async_example();
        binary_example();
        multi_sink_example();
        user_defined_example();
        err_handler_example();
        trace_example();
        stopwatch_example();
        custom_flags_example();
 
        // Flush all *registered* loggers using a worker thread every 3 seconds.
        // note: registered loggers *must* be thread safe for this to work correctly!
        spdlog::flush_every(std::chrono::seconds(3));
 
        // Apply some function on all registered loggers
        spdlog::apply_all([&](std::shared_ptr<spdlog::logger> l) { l->info("End of example."); });
 
        // Release all spdlog resources, and drop all loggers in the registry.
        // This is optional (only mandatory if using windows + async log).
        spdlog::shutdown();
    }
 
    // Exceptions will only be thrown upon failed logger or sink construction (not during logging).
    catch (const spdlog::spdlog_ex &ex)
    {
        std::printf("Log initialization failed: %s\n", ex.what());
        return 1;
    }
}
 
#include "spdlog/sinks/stdout_color_sinks.h"
// or #include "spdlog/sinks/stdout_sinks.h" if no colors needed.
void stdout_logger_example()
{
    // Create color multi threaded logger.
    auto console = spdlog::stdout_color_mt("console");
    // or for stderr:
    // auto console = spdlog::stderr_color_mt("error-logger");
}
 
#include "spdlog/sinks/basic_file_sink.h"
void basic_example()
{
    // Create basic file logger (not rotated).
    auto my_logger = spdlog::basic_logger_mt("file_logger", "logs/basic-log.txt");
}
 
#include "spdlog/sinks/rotating_file_sink.h"
void rotating_example()
{
    // Create a file rotating logger with 5mb size max and 3 rotated files.
    auto rotating_logger = spdlog::rotating_logger_mt("some_logger_name", "logs/rotating.txt", 1048576 * 5, 3);
}
 
#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 daily_logger = spdlog::daily_logger_mt("daily_logger", "logs/daily.txt", 2, 30);
}
 
#include "spdlog/cfg/env.h"
void load_levels_example()
{
    // Set the log level to "info" and mylogger to "trace":
    // SPDLOG_LEVEL=info,mylogger=trace && ./example
    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(args, argv);
}
 
#include "spdlog/async.h"
void async_example()
{
    // Default thread pool settings can be modified *before* creating the async logger:
    // spdlog::init_thread_pool(32768, 1); // queue with max 32k items 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");
 
    for (int i = 1; i < 101; ++i)
    {
        async_file->info("Async message #{}", i);
    }
}
 
// Log binary data as hex.
// Many types of std::container<char> types can be used.
// Iterator 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()
{
    std::vector<char> buf(80);
    for (int i = 0; i < 80; i++)
    {
        buf.push_back(static_cast<char>(i & 0xff));
    }
    spdlog::info("Binary example: {}", spdlog::to_hex(buf));
    spdlog::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));
    // logger->info("hexdump style: {:a}", spdlog::to_hex(buf));
    // logger->info("hexdump style, 20 chars per line {:a}", spdlog::to_hex(buf, 20));
}
 
// Compile time log levels.
// define SPDLOG_ACTIVE_LEVEL to required level (e.g. SPDLOG_LEVEL_TRACE)
void trace_example()
{
    // trace from default logger
    SPDLOG_TRACE("Some trace message.. {} ,{}", 1, 3.23);
    // debug from default logger
    SPDLOG_DEBUG("Some debug message.. {} ,{}", 1, 3.23);
 
    // trace from logger object
    auto logger = spdlog::get("file_logger");
    SPDLOG_LOGGER_TRACE(logger, "another trace message");
}
 
// stopwatch example
#include "spdlog/stopwatch.h"
#include <thread>
void stopwatch_example()
{
    spdlog::stopwatch sw;
    std::this_thread::sleep_for(std::chrono::milliseconds(123));
    spdlog::info("Stopwatch: {} seconds", sw);
}
 
// A logger with multiple sinks (stdout and file) - each with a different format and log level.
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");
}
 
// User defined types logging by implementing operator<<
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::info("user defined type: {}", my_type{14});
}
 
// Custom error handler. Will be triggered on log failure.
void err_handler_example()
{
    // can be set globally or per logger(logger->set_error_handler(..))
    spdlog::set_error_handler([](const std::string &msg) { printf("*** Custom log error handler: %s ***\n", msg.c_str()); });
}
 
// syslog example (linux/osx/freebsd)
#ifndef _WIN32
#    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.");
}
#endif
 
// Android example.
#if defined(__ANDROID__)
#    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.");
}
#endif
 
// Log patterns can contain custom flags.
// this will add custom 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()
{
 
    using spdlog::details::make_unique; // for pre c++14
    auto formatter = make_unique<spdlog::pattern_formatter>();
    formatter->add_flag<my_formatter_flag>('*').set_pattern("[%n] [%*] [%^%l%$] %v");
    spdlog::set_formatter(std::move(formatter));
}