C++编写单实例运行的程序

有些程序要求只运行一个实例, 实现单实例的方法也有多种, 之前我一般是通过锁住一个pid文件实现单实例运行, 最近在网上看到绑定套接字的方法实现单实例运行，这种方法在程序退出时候能够自动释放套接字, 实现了自我清理的过程, 很是优雅。

//singleton.h

#include <iostream>
#include <string>

class Singleton
{
public:
    Singleton(uint16_t port) : socket_fd_(-1), rc_(1), port_(port)
    {}

    ~Singleton();

    bool operator()();

private:
    int socket_fd_ = -1;
    int rc_;
    uint16_t port_;
};
        

//singleton.cpp

#include <unistd.h>
#include <string.h>
#include <netinet/in.h>
#include "singleton.h"

Singleton::~Singleton()
{
    if (socket_fd_ != -1) {
        close(socket_fd_);
    }
}

bool Singleton::operator()()
{
    if (socket_fd_ == -1 || rc_) {
        socket_fd_ = -1;
        rc_ = 1;

        if ((socket_fd_ = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
            throw std::runtime_error(std::string("could not create socket: ") + strerror(errno));
        } else {
            struct sockaddr_in name;
            name.sin_family = AF_INET;
            name.sin_port = htons(port_);
            name.sin_addr.s_addr = htonl(INADDR_ANY);
            rc_ = bind(socket_fd_, (struct sockaddr *) &name, sizeof(name));
        }
    }

    return (socket_fd_ != -1 && rc_ == 0);
}

//main.cpp

#include <iostream>
#include "singleton.h"

int main(int argc, char *argv[])
{
    const int port = 5678;
    Singleton single(port);

    if (!single()) {
        std::cerr << "program already running." << std::endl;
        exit(-1);
    }

    while (true) {
        // keep program do not return
        ;
    }

    return 0;
}