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502 lines
17 KiB
Markdown
502 lines
17 KiB
Markdown
# spdlog
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Very fast, header-only/compiled, C++ logging library. [](https://github.com/gabime/spdlog/actions/workflows/ci.yml) [](https://ci.appveyor.com/project/gabime/spdlog) [](https://github.com/gabime/spdlog/releases/latest)
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## Install
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#### Header-only version
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Copy the include [folder](https://github.com/gabime/spdlog/tree/v2.x/include/spdlog) to your build tree and use a C++17 compiler.
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#### Compiled version (recommended - much faster compile times)
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```console
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$ git clone https://github.com/gabime/spdlog.git
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$ cd spdlog && mkdir build && cd build
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$ cmake .. && make -j
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```
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see example [CMakeLists.txt](https://github.com/gabime/spdlog/blob/v2.x/example/CMakeLists.txt) on how to use.
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## Platforms
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* Linux, FreeBSD, OpenBSD, Solaris, AIX
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* Windows (msvc, cygwin)
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* macOS
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* Android
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## Package managers:
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* Debian: `sudo apt install libspdlog-dev`
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* Homebrew: `brew install spdlog`
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* MacPorts: `sudo port install spdlog`
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* FreeBSD: `pkg install spdlog`
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* Fedora: `dnf install spdlog`
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* Gentoo: `emerge dev-libs/spdlog`
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* Arch Linux: `pacman -S spdlog`
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* openSUSE: `sudo zypper in spdlog-devel`
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* vcpkg: `vcpkg install spdlog`
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* conan: `spdlog/[>=1.4.1]`
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* conda: `conda install -c conda-forge spdlog`
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* build2: ```depends: spdlog ^1.8.2```
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## Features
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* Very fast (see [benchmarks](#benchmarks) below).
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* Headers only or compiled
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* Feature-rich formatting, using the excellent [fmt](https://github.com/fmtlib/fmt) library.
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* Asynchronous mode (optional)
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* [Custom](https://github.com/gabime/spdlog/wiki/3.-Custom-formatting) formatting.
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* Multi/Single threaded loggers.
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* Various log targets:
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* Rotating log files.
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* Daily log files.
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* Console logging (colors supported).
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* syslog.
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* Windows event log.
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* Windows debugger (```OutputDebugString(..)```).
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* Log to Qt widgets ([example](#log-to-qt-with-nice-colors)).
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* Easily [extendable](https://github.com/gabime/spdlog/wiki/4.-Sinks#implementing-your-own-sink) with custom log targets.
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* Log filtering - log levels can be modified at runtime as well as compile time.
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* Support for loading log levels from argv or environment var.
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* [Backtrace](#backtrace-support) support - store debug messages in a ring buffer and display them later on demand.
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## Usage samples
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#### Basic usage
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```c++
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#include "spdlog/spdlog.h"
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int main()
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{
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spdlog::info("Welcome to spdlog!");
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spdlog::error("Some error message with arg: {}", 1);
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spdlog::warn("Easy padding in numbers like {:08d}", 12);
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spdlog::critical("Support for int: {0:d}; hex: {0:x}; oct: {0:o}; bin: {0:b}", 42);
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spdlog::info("Support for floats {:03.2f}", 1.23456);
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spdlog::info("Positional args are {1} {0}..", "too", "supported");
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spdlog::info("{:<30}", "left aligned");
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spdlog::set_level(spdlog::level::debug); // Set global log level to debug
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spdlog::debug("This message should be displayed..");
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// change log pattern
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spdlog::set_pattern("[%H:%M:%S %z] [%n] [%^---%L---%$] [thread %t] %v");
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// Compile time log levels
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// define SPDLOG_ACTIVE_LEVEL to desired level
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SPDLOG_TRACE("Some trace message with param {}", 42);
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SPDLOG_DEBUG("Some debug message");
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}
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```
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---
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#### Create stdout/stderr logger object
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```c++
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#include "spdlog/spdlog.h"
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#include "spdlog/sinks/stdout_color_sinks.h"
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void stdout_example()
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{
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// create a color multi-threaded logger
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auto console = spdlog::stdout_color_mt("console");
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auto err_logger = spdlog::stderr_color_mt("stderr");
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spdlog::get("console")->info("loggers can be retrieved from a global registry using the spdlog::get(logger_name)");
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}
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```
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---
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#### Basic file logger
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```c++
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#include "spdlog/sinks/basic_file_sink.h"
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void basic_logfile_example()
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{
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try
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{
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auto logger = spdlog::basic_logger_mt("basic_logger", "logs/basic-log.txt");
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}
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catch (const spdlog::spdlog_ex &ex)
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{
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std::cout << "Log init failed: " << ex.what() << std::endl;
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}
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}
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```
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---
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#### Rotating files
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```c++
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#include "spdlog/sinks/rotating_file_sink.h"
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void rotating_example()
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{
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// Create a file rotating logger with 5 MB size max and 3 rotated files
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auto max_size = 1048576 * 5;
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auto max_files = 3;
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auto logger = spdlog::rotating_logger_mt("some_logger_name", "logs/rotating.txt", max_size, max_files);
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}
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```
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---
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#### Daily files
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```c++
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#include "spdlog/sinks/daily_file_sink.h"
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void daily_example()
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{
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// Create a daily logger - a new file is created every day at 2:30 am
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auto logger = spdlog::daily_logger_mt("daily_logger", "logs/daily.txt", 2, 30);
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}
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```
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---
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#### Backtrace support
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```c++
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// Debug messages can be stored in a ring buffer instead of being logged immediately.
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// This is useful to display debug logs only when needed (e.g. when an error happens).
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// When needed, call dump_backtrace() to dump them to your log.
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spdlog::enable_backtrace(32); // Store the latest 32 messages in a buffer.
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// or my_logger->enable_backtrace(32)..
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for(int i = 0; i < 100; i++)
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{
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spdlog::debug("Backtrace message {}", i); // not logged yet..
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}
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// e.g. if some error happened:
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spdlog::dump_backtrace(); // log them now! show the last 32 messages
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// or my_logger->dump_backtrace(32)..
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```
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---
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#### Periodic flush
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```c++
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// periodically flush all *registered* loggers every 3 seconds:
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// warning: only use if all your loggers are thread-safe ("_mt" loggers)
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spdlog::flush_every(std::chrono::seconds(3));
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```
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---
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#### Stopwatch
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```c++
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// Stopwatch support for spdlog
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#include "spdlog/stopwatch.h"
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void stopwatch_example()
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{
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spdlog::stopwatch sw;
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spdlog::debug("Elapsed {}", sw);
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spdlog::debug("Elapsed {:.3}", sw);
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}
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```
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---
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#### Log binary data in hex
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```c++
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// many types of std::container<char> types can be used.
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// ranges are supported too.
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// format flags:
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// {:X} - print in uppercase.
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// {:s} - don't separate each byte with space.
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// {:p} - don't print the position on each line start.
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// {:n} - don't split the output into lines.
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// {:a} - show ASCII if :n is not set.
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#include "spdlog/fmt/bin_to_hex.h"
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void binary_example()
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{
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auto console = spdlog::get("console");
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std::array<char, 80> buf;
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console->info("Binary example: {}", spdlog::to_hex(buf));
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console->info("Another binary example:{:n}", spdlog::to_hex(std::begin(buf), std::begin(buf) + 10));
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// more examples:
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// logger->info("uppercase: {:X}", spdlog::to_hex(buf));
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// logger->info("uppercase, no delimiters: {:Xs}", spdlog::to_hex(buf));
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// logger->info("uppercase, no delimiters, no position info: {:Xsp}", spdlog::to_hex(buf));
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}
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```
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---
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#### Logger with multi sinks - each with a different format and log level
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```c++
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// create a logger with 2 targets, with different log levels and formats.
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// The console will show only warnings or errors, while the file will log all.
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void multi_sink_example()
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{
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auto console_sink = std::make_shared<spdlog::sinks::stdout_color_sink_mt>();
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console_sink->set_level(spdlog::level::warn);
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console_sink->set_pattern("[multi_sink_example] [%^%l%$] %v");
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auto file_sink = std::make_shared<spdlog::sinks::basic_file_sink_mt>("logs/multisink.txt", true);
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file_sink->set_level(spdlog::level::trace);
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spdlog::logger logger("multi_sink", {console_sink, file_sink});
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logger.set_level(spdlog::level::debug);
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logger.warn("this should appear in both console and file");
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logger.info("this message should not appear in the console, only in the file");
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}
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```
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---
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#### User-defined callbacks about log events
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```c++
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// create a logger with a lambda function callback, the callback will be called
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// each time something is logged to the logger
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void callback_example()
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{
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auto callback_sink = std::make_shared<spdlog::sinks::callback_sink_mt>([](const spdlog::details::log_msg &msg) {
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// for example you can be notified by sending an email to yourself
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});
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callback_sink->set_level(spdlog::level::err);
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auto console_sink = std::make_shared<spdlog::sinks::stdout_color_sink_mt>();
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spdlog::logger logger("custom_callback_logger", {console_sink, callback_sink});
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logger.info("some info log");
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logger.error("critical issue"); // will notify you
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}
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```
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---
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#### Asynchronous logging
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```c++
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#include "spdlog/async.h"
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#include "spdlog/sinks/basic_file_sink.h"
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void async_example()
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{
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// default thread pool settings can be modified *before* creating the async logger:
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// spdlog::init_thread_pool(8192, 1); // queue with 8k items and 1 backing thread.
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auto async_file = spdlog::basic_logger_mt<spdlog::async_factory>("async_file_logger", "logs/async_log.txt");
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// alternatively:
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// auto async_file = spdlog::create_async<spdlog::sinks::basic_file_sink_mt>("async_file_logger", "logs/async_log.txt");
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}
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```
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---
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#### Asynchronous logger with multi sinks
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```c++
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#include "spdlog/sinks/stdout_color_sinks.h"
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#include "spdlog/sinks/rotating_file_sink.h"
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void multi_sink_example2()
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{
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spdlog::init_thread_pool(8192, 1);
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auto stdout_sink = std::make_shared<spdlog::sinks::stdout_color_sink_mt >();
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auto rotating_sink = std::make_shared<spdlog::sinks::rotating_file_sink_mt>("mylog.txt", 1024*1024*10, 3);
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std::vector<spdlog::sink_ptr> sinks {stdout_sink, rotating_sink};
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auto logger = std::make_shared<spdlog::async_logger>("loggername", sinks.begin(), sinks.end(), spdlog::thread_pool(), spdlog::async_overflow_policy::block);
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spdlog::register_logger(logger);
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}
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```
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---
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#### User-defined types
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```c++
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template<>
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struct fmt::formatter<my_type> : fmt::formatter<std::string>
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{
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auto format(my_type my, format_context &ctx) const -> decltype(ctx.out())
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{
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return format_to(ctx.out(), "[my_type i={}]", my.i);
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}
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};
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void user_defined_example()
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{
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spdlog::info("user defined type: {}", my_type(14));
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}
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```
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---
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#### User-defined flags in the log pattern
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```c++
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// Log patterns can contain custom flags.
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// the following example will add new flag '%*' - which will be bound to a <my_formatter_flag> instance.
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#include "spdlog/pattern_formatter.h"
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class my_formatter_flag : public spdlog::custom_flag_formatter
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{
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public:
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void format(const spdlog::details::log_msg &, const std::tm &, spdlog::memory_buf_t &dest) override
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{
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std::string some_txt = "custom-flag";
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dest.append(some_txt.data(), some_txt.data() + some_txt.size());
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}
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std::unique_ptr<custom_flag_formatter> clone() const override
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{
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return std::make_unique<my_formatter_flag>();
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}
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};
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void custom_flags_example()
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{
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auto formatter = std::make_unique<spdlog::pattern_formatter>();
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formatter->add_flag<my_formatter_flag>('*').set_pattern("[%n] [%*] [%^%l%$] %v");
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spdlog::set_formatter(std::move(formatter));
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}
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```
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---
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#### Custom error handler
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```c++
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void err_handler_example()
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{
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// can be set globally or per logger(logger->set_error_handler(..))
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spdlog::set_error_handler([](const std::string &msg) { spdlog::get("console")->error("*** LOGGER ERROR ***: {}", msg); });
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spdlog::get("console")->info("some invalid message to trigger an error {}{}{}{}", 3);
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}
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```
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---
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#### syslog
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```c++
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#include "spdlog/sinks/syslog_sink.h"
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void syslog_example()
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{
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std::string ident = "spdlog-example";
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auto syslog_logger = spdlog::syslog_logger_mt("syslog", ident, LOG_PID);
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syslog_logger->warn("This is warning that will end up in syslog.");
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}
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```
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---
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#### Android example
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```c++
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#include "spdlog/sinks/android_sink.h"
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void android_example()
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{
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std::string tag = "spdlog-android";
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auto android_logger = spdlog::android_logger_mt("android", tag);
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android_logger->critical("Use \"adb shell logcat\" to view this message.");
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}
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```
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---
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#### Load log levels from the env variable or argv
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```c++
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#include "spdlog/cfg/env.h"
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int main (int argc, char *argv[])
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{
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spdlog::cfg::load_env_levels();
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// or from the command line:
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// ./example SPDLOG_LEVEL=info,mylogger=trace
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// #include "spdlog/cfg/argv.h" // for loading levels from argv
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// spdlog::cfg::load_argv_levels(argc, argv);
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}
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```
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So then you can:
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```console
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$ export SPDLOG_LEVEL=info,mylogger=trace
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$ ./example
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```
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---
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#### Log file open/close event handlers
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```c++
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// You can get callbacks from spdlog before/after a log file has been opened or closed.
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// This is useful for cleanup procedures or for adding something to the start/end of the log file.
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void file_events_example()
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{
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// pass the spdlog::file_event_handlers to file sinks for open/close log file notifications
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spdlog::file_event_handlers handlers;
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handlers.before_open = [](spdlog::filename_t filename) { spdlog::info("Before opening {}", filename); };
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handlers.after_open = [](spdlog::filename_t filename, std::FILE *fstream) { fputs("After opening\n", fstream); };
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handlers.before_close = [](spdlog::filename_t filename, std::FILE *fstream) { fputs("Before closing\n", fstream); };
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handlers.after_close = [](spdlog::filename_t filename) { spdlog::info("After closing {}", filename); };
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auto my_logger = spdlog::basic_logger_st("some_logger", "logs/events-sample.txt", true, handlers);
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}
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```
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---
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#### Replace the Default Logger
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```c++
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void replace_default_logger_example()
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{
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auto new_logger = spdlog::basic_logger_mt("new_default_logger", "logs/new-default-log.txt", true);
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spdlog::set_default_logger(new_logger);
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spdlog::info("new logger log message");
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}
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```
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---
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#### Log to Qt with nice colors
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```c++
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#include "spdlog/spdlog.h"
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#include "spdlog/sinks/qt_sinks.h"
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MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
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{
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setMinimumSize(640, 480);
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auto log_widget = new QTextEdit(this);
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setCentralWidget(log_widget);
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int max_lines = 500; // keep the text widget to max 500 lines. remove old lines if needed.
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auto logger = spdlog::qt_color_logger_mt("qt_logger", log_widget, max_lines);
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logger->info("Some info message");
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}
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```
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---
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## Benchmarks
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Below are some [benchmarks](https://github.com/gabime/spdlog/blob/v2.x/bench/bench.cpp) done in Ubuntu 64 bit, Intel i7-4770 CPU @ 3.40GHz
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#### Synchronous mode
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```
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[info] **************************************************************
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[info] Single thread, 1,000,000 iterations
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[info] **************************************************************
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[info] basic_st Elapsed: 0.17 secs 5,777,626/sec
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[info] rotating_st Elapsed: 0.18 secs 5,475,894/sec
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[info] daily_st Elapsed: 0.20 secs 5,062,659/sec
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[info] empty_logger Elapsed: 0.07 secs 14,127,300/sec
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[info] **************************************************************
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[info] C-string (400 bytes). Single thread, 1,000,000 iterations
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[info] **************************************************************
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[info] basic_st Elapsed: 0.41 secs 2,412,483/sec
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[info] rotating_st Elapsed: 0.72 secs 1,389,196/sec
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[info] daily_st Elapsed: 0.42 secs 2,393,298/sec
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[info] null_st Elapsed: 0.04 secs 27,446,957/sec
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[info] **************************************************************
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[info] 10 threads, competing over the same logger object, 1,000,000 iterations
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[info] **************************************************************
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[info] basic_mt Elapsed: 0.60 secs 1,659,613/sec
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[info] rotating_mt Elapsed: 0.62 secs 1,612,493/sec
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[info] daily_mt Elapsed: 0.61 secs 1,638,305/sec
|
|
[info] null_mt Elapsed: 0.16 secs 6,272,758/sec
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|
```
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|
#### Asynchronous mode
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|
```
|
|
[info] -------------------------------------------------
|
|
[info] Messages : 1,000,000
|
|
[info] Threads : 10
|
|
[info] Queue : 8,192 slots
|
|
[info] Queue memory : 8,192 x 272 = 2,176 KB
|
|
[info] -------------------------------------------------
|
|
[info]
|
|
[info] *********************************
|
|
[info] Queue Overflow Policy: block
|
|
[info] *********************************
|
|
[info] Elapsed: 1.70784 secs 585,535/sec
|
|
[info] Elapsed: 1.69805 secs 588,910/sec
|
|
[info] Elapsed: 1.7026 secs 587,337/sec
|
|
[info]
|
|
[info] *********************************
|
|
[info] Queue Overflow Policy: overrun
|
|
[info] *********************************
|
|
[info] Elapsed: 0.372816 secs 2,682,285/sec
|
|
[info] Elapsed: 0.379758 secs 2,633,255/sec
|
|
[info] Elapsed: 0.373532 secs 2,677,147/sec
|
|
|
|
```
|
|
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|
## Documentation
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|
Documentation can be found in the [wiki](https://github.com/gabime/spdlog/wiki/1.-QuickStart) pages.
|
|
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---
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Thanks to [JetBrains](https://www.jetbrains.com/?from=spdlog) for donating product licenses to help develop **spdlog** <a href="https://www.jetbrains.com/?from=spdlog"><img src="logos/jetbrains-variant-4.svg" width="94" align="center" /></a>
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