写一个获取本地ip的linux和Windows的c++实现

获取本地IP地址可以通过编写 C++ 程序来实现，下面分别给出在 Linux 和 Windows 操作系统下获取本地IP地址的实现。

在 Linux 下实现：

#include <iostream>
#include <string>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <ifaddrs.h>

int main() {
    struct ifaddrs *ifAddrStruct = nullptr;
    struct ifaddrs *ifa = nullptr;
    void *tmpAddrPtr = nullptr;

    getifaddrs(&ifAddrStruct);

    std::string localIpAddress;

    for (ifa = ifAddrStruct; ifa != nullptr; ifa = ifa->ifa_next) {
        if (!ifa->ifa_addr) {
            continue;
        }
        if (ifa->ifa_addr->sa_family == AF_INET) { // IPv4 Address
            tmpAddrPtr = &((struct sockaddr_in *)ifa->ifa_addr)->sin_addr;
            char addressBuffer[INET_ADDRSTRLEN];
            inet_ntop(AF_INET, tmpAddrPtr, addressBuffer, INET_ADDRSTRLEN);
            localIpAddress = addressBuffer;
            std::cout << "IP Address: " << localIpAddress << std::endl;
        }
    }

    if (ifAddrStruct != nullptr) {
        freeifaddrs(ifAddrStruct);
    }

    return 0;
}

在 Windows 下实现：

#include <iostream>
#include <string>
#include <winsock2.h>
#include <iphlpapi.h>
#pragma comment(lib, "iphlpapi.lib")

int main() {
    ULONG bufferSize = 0;

    GetAdaptersAddresses(AF_UNSPEC, GAA_FLAG_INCLUDE_PREFIX, nullptr, nullptr, &bufferSize);

    PIP_ADAPTER_ADDRESSES adapterAddresses = (PIP_ADAPTER_ADDRESSES) malloc(bufferSize);

    GetAdaptersAddresses(AF_UNSPEC, GAA_FLAG_INCLUDE_PREFIX, nullptr, adapterAddresses, &bufferSize);

    std::string localIpAddress;

    PIP_ADAPTER_ADDRESSES adapterAddress = adapterAddresses;
    while (adapterAddress) {
        if (adapterAddress->OperStatus == IfOperStatusUp) {
            PIP_ADAPTER_UNICAST_ADDRESS unicastAddress = adapterAddress->FirstUnicastAddress;
            while (unicastAddress) {
                if (unicastAddress->Address.lpSockaddr->sa_family == AF_INET) {
                    char addressBuffer[INET_ADDRSTRLEN];
                    inet_ntop(AF_INET, &((struct sockaddr_in*)unicastAddress->Address.lpSockaddr)->sin_addr, addressBuffer, INET_ADDRSTRLEN);
                    localIpAddress = addressBuffer;
                    std::cout << "IP Address: " << localIpAddress << std::endl;
                }
                unicastAddress = unicastAddress->Next;
            }
        }
        adapterAddress = adapterAddress->Next;
    }

    free(adapterAddresses);

    return 0;
}

需要注意的是，在 Windows 下需要链接 `iphlpapi.lib` 库。