C++在Rdis里面使用redisCommand查看key的list长度

可以使用以下代码：

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

int main() {
    // Connect to Redis server
    redisContext* redis = redisConnect("127.0.0.1", 6379);
    if(redis == NULL || redis->err) {
        std::cout << "Error connecting to Redis server: " << redis->errstr << std::endl;
        exit(EXIT_FAILURE);
    }

    // Use redisCommand to get list length
    redisReply* reply = (redisReply*)redisCommand(redis, "LLEN mylist");
    if(reply == NULL) {
        std::cout << "Error getting list length: " << redis->errstr << std::endl;
        exit(EXIT_FAILURE);
    }

    // Print list length
    std::cout << "List length: " << reply->integer << std::endl;

    // Free reply and disconnect from Redis server
    freeReplyObject(reply);
    redisFree(redis);

    return 0;
}

其中，redisCommand(redis, "LLEN mylist")会执行Redis命令"LLEN mylist"来获取列表"mylist"的长度，返回值为redisReply*类型的指针。需要注意的是，在使用完redisCommand返回的redisReply*之后，需要使用freeReplyObject函数来释放内存空间