Using spdlog in a C++ project

Tree structure of the project.

The code of main.cc.

#include <iostream>
#include "spdlog/spdlog.h"
#include "spdlog/sinks/basic_file_sink.h"
#include "spdlog/sinks/rotating_file_sink.h"

void do_work_in_another_file();
void rotating_example()
{
    try
    {
        // Create a file rotating logger with 5 MB size max and 3 rotated files
        auto max_size = 1048576 * 5;
        auto max_files = 3;

        // Set output time pattern
        // %f: Time accurate to microseconds
        // %n: Output mode "some_logger_name"
        // %l: Prints the severity level of the log message. Example include info, warn, error, debug or critical.
        // %v:  Prints the actual text or payload of the log message that you passed to the function.
        spdlog::set_pattern("[%Y-%m-%d %H:%M:%S.%f] [%n] [%l] %v");

        // Set it as default so you can spdlog::info() directly.
        auto logger = spdlog::rotating_logger_mt("some_logger_name",
                "logs/rotating.txt", max_size, max_files);

        logger->info("This is a log message that will trigger rotation once the file is full.");

        } catch (const spdlog::spdlog_ex& ex){
            std::cerr << "Log initialization failed:" << ex.what() << std::endl;
    }
}

int main(void)
{
    rotating_example();
    do_work_in_another_file();
    return 0;
}

The code of test.cc.

#include "spdlog/spdlog.h"

void do_work_in_another_file()
{
    // Get the logger by its registered name
    auto logger = spdlog::get("some_logger_name");
    if (logger) {
        logger->info("This message come from another file!");
    }
}

The output log:

Attention:
Spdlog print the info level log by default. If you want to print the debug level log, you need to set the spdlog default level. As follows:

spdlog::set_level(spdlog::level::debug);

Multiple log file must set in the main.cc or spdlog will show error message, as following:

$ cmake --build .
[1/2] Building CXX object CMakeFiles/my_app.dir/sma.cc.o
FAILED: [code=1] CMakeFiles/my_app.dir/sma.cc.o
/ucrt64/bin/g++.exe  -I/d/cc/ex1/third_party/spdlog/include -std=gnu++11 -MD -MT CMakeFiles/my_app.dir/sma.cc.o -MF CMakeFiles/my_app.dir/sma.cc.o.d -o CMakeFiles/my_app.dir/sma.cc.o -c /d/cc/ex1/sma.cc
D:/cc/ex1/sma.cc: In function 'double Sma(const std::vector&, int)':
D:/cc/ex1/sma.cc:30:9: error: 'log_sma' was not declared in this scope
   30 |         log_sma->info("The size of prices={} less than period={}!",

Eliminate errors, you should declare all log files in main.cc:

void rotating_example()
{
    try
    {
        // Create a file rotating logger with 5 MB size max and 3 rotated files
        auto max_size = 1048576 * 5; // 5M
        auto max_files = 8;

        // Set output time pattern
        // %f: Time accurate to microseconds
        // %n: Output mode "some_logger_name"
        // %l: Prints the severity level of the log message. Example include info, warn, error, debug or critical.
        // %v:  Prints the actual text or payload of the log message that you passed to the function.
        spdlog::set_pattern("[%Y-%m-%d %H:%M:%S.%f] [%n] [%l] %v");

        // Set it as default so you can spdlog::info() directly.
        auto logger = spdlog::rotating_logger_mt("some_logger_name",
                "logs/rotating.txt", max_size, max_files);

        auto log_sma = spdlog::rotating_logger_mt("SMA",
                "logs/sma_log.txt", max_size, max_files);
        logger->info("This is a log message that will trigger rotation once the file is full.");

        } catch (const spdlog::spdlog_ex& ex){
            std::cerr << "Log initialization failed:" << ex.what() << std::endl;
    }
}

Getting "SMA" logger in sma.cc:

#include "spdlog/spdlog.h"
#include "spdlog/sinks/basic_file_sink.h"
#include "spdlog/sinks/rotating_file_sink.h"
#include <numeric>
#include <iostream>

// Function to calculate Simple Moving Average
double Sma(const std::vector &prices, int period){
    auto logger = spdlog::get("SMA");
    if (logger) {
        logger->info("Getting logger succeed!");
    }

    if (prices.size() > period) {
        logger->info("The size of prices={} less than period={}!",
                prices.size(), period);
        return 0.0;
    }

    // Sum the last 'period' elements
    double sum = std::accumulate(prices.end() - period, prices.end(),0);
    return sum / period;
}