README.md

💂 guardpp

A C++17 library for single-instance applications

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⚙️ Configuration

Tests

set(guardpp_tests OFF)

If set to ON, guardpp will build a test executable.

📎 Installation

• FetchContent

  include(FetchContent)
  FetchContent_Declare(lockpp GIT_REPOSITORY "https://github.com/Soundux/guardpp")
  
  FetchContent_MakeAvailable(guardpp)
  target_link_libraries(<YourLibrary> guardpp)

• Git Submodule

  git submodule add "https://github.com/Soundux/guardpp"

  # Somewhere in your CMakeLists.txt
  add_subdirectory("<path_to_guardpp>")
  target_link_libraries(<YourLibrary> guardpp)

📔 Usage

Example

#include <guard.hpp>
#include <iostream>

int main()
{
    guardpp::guard instance_guard("guardpp");

    auto other_instance = instance_guard.other_instance();
    
    if (other_instance)
    {
        if (other_instance.value())
        {
            std::cout << "Another instance is running!" << std::endl;
        }
        else
        {
            std::cout << "No other instance is running!" << std::endl;
        }
    }
    else
    {
        std::cout << other_instance.error() << std::endl;
    }

    // You can also take-over an existing lock by calling instance_guard.reset(); 
}

📚 Dependencies

• expected
• tiny-process-library (For tests only!)

ℹ️ Remarks

• guard::reset() is unimplemented on Windows. This is because on Windows a mutex can only be deleted by closing all existing handles to the mutex, we can not do this because we can't access the handles created by other processes.¹

• The linux implementation now uses file based locks instead of shared memory / semaphores, because they seem to be more robust.²

¹ https://stackoverflow.com/questions/9072570/how-can-i-delete-a-mutex-and-semaphore-in-win32-api
² http://charette.no-ip.com:81/programming/2010-01-13_PosixSemaphores/index.html