如何在C++中使用SFTP和libssh从服务器下载文件夹或文件？

#include <libssh/libssh.h>
#include <iostream>

int main()
{
    // 初始化ssh会话
    ssh_session my_ssh_session = ssh_new();
    if (my_ssh_session == NULL)
    {
        std::cout << "Failed to create SSH session." << std::endl;
        return 1;
    }

    // 设置服务器连接信息
    ssh_options_set(my_ssh_session, SSH_OPTIONS_HOST, "服务器IP地址");
    ssh_options_set(my_ssh_session, SSH_OPTIONS_USER, "用户名");

    // 连接服务器
    int connect_result = ssh_connect(my_ssh_session);
    if (connect_result != SSH_OK)
    {
        std::cout << "Failed to connect to server." << std::endl;
        ssh_free(my_ssh_session);
        return 1;
    }

    // 验证服务器
    int verify_result = ssh_userauth_password(my_ssh_session, NULL, "密码");
    if (verify_result != SSH_AUTH_SUCCESS)
    {
        std::cout << "Failed to authenticate to server." << std::endl;
        ssh_disconnect(my_ssh_session);
        ssh_free(my_ssh_session);
        return 1;
    }

    // 连接成功，可以进行后续操作

    // 关闭连接
    ssh_disconnect(my_ssh_session);
    ssh_free(my_ssh_session);

    return 0;
}

#include <libssh/libssh.h>
#include <iostream>

int main()
{
    // 初始化ssh会话
    ssh_session my_ssh_session = ssh_new();
    if (my_ssh_session == NULL)
    {
        std::cout << "Failed to create SSH session." << std::endl;
        return 1;
    }

    // 设置服务器连接信息
    ssh_options_set(my_ssh_session, SSH_OPTIONS_HOST, "服务器IP地址");
    ssh_options_set(my_ssh_session, SSH_OPTIONS_USER, "用户名");

    // 连接服务器
    int connect_result = ssh_connect(my_ssh_session);
    if (connect_result != SSH_OK)
    {
        std::cout << "Failed to connect to server." << std::endl;
        ssh_free(my_ssh_session);
        return 1;
    }

    // 验证服务器
    int verify_result = ssh_userauth_password(my_ssh_session, NULL, "密码");
    if (verify_result != SSH_AUTH_SUCCESS)
    {
        std::cout << "Failed to authenticate to server." << std::endl;
        ssh_disconnect(my_ssh_session);
        ssh_free(my_ssh_session);
        return 1;
    }

    // SFTP会话
    sftp_session sftp = sftp_new(my_ssh_session);
    if (sftp == NULL)
    {
        std::cout << "Failed to create SFTP session." << std::endl;
        ssh_disconnect(my_ssh_session);
        ssh_free(my_ssh_session);
        return 1;
    }

    // 打开SFTP会话
    int sftp_init_result = sftp_init(sftp);
    if (sftp_init_result != SSH_OK)
    {
        std::cout << "Failed to initialize SFTP session." << std::endl;
        sftp_free(sftp);
        ssh_disconnect(my_ssh_session);
        ssh_free(my_ssh_session);
        return 1;
    }

    // 下载文件或文件夹
    const char* remote_path = "/服务器上的文件或文件夹路径";
    const char* local_path = "/本地保存路径";
    sftp_file file = sftp_open(sftp, remote_path, O_RDONLY, 0);
    if (file == NULL)
    {
        std::cout << "Failed to open file." << std::endl;
        sftp_free(sftp);
        ssh_disconnect(my_ssh_session);
        ssh_free(my_ssh_session);
        return 1;
    }

    char buffer[8192];
    ssize_t nbytes, nwritten;
    FILE* local_file = fopen(local_path, "wb");
    while ((nbytes = sftp_read(file, buffer, sizeof(buffer))) > 0)
    {
        nwritten = fwrite(buffer, 1, nbytes, local_file);
        if (nwritten != nbytes)
        {
            std::cout << "Failed to write to local file." << std::endl;
            sftp_close(file);
            sftp_free(sftp);
            ssh_disconnect(my_ssh_session);
            ssh_free(my_ssh_session);
            fclose(local_file);
            return 1;
        }
    }

    sftp_close(file);
    sftp_free(sftp);

    // 关闭连接
    ssh_disconnect(my_ssh_session);
    ssh_free(my_ssh_session);

    fclose(local_file);

    return 0;
}