Redis 是完全开源免费的，遵守BSD协议，先进的key - value持久化产品。它通常被称为数据结构服务器，因为值（value）可以是 字符串(String), 哈希(Map), 列表(list), 集合(sets) 和 有序集合(sorted sets)等类型。

redis客户端连接比较简单，但日常中redis的使用和维护会有很多地方需要学习。本文只简单介绍下常用函数。

//hiredis/hiredis.h

/* Context for a connection to Redis */

typedef struct redisContext {

    int err; /* Error flags, 0 when there is no error */

    char errstr[128]; /* String representation of error when applicable */

    int fd;

    int flags;

    char *obuf; /* Write buffer */

    redisReader *reader; /* Protocol reader */

} redisContext;

/* This is the reply object returned by redisCommand() */

#define REDIS_REPLY_STRING 1

#define REDIS_REPLY_ARRAY 2

#define REDIS_REPLY_INTEGER 3

#define REDIS_REPLY_NIL 4

#define REDIS_REPLY_STATUS 5

#define REDIS_REPLY_ERROR 6

typedef struct redisReply {

    int type; /* REDIS_REPLY_* */

    long long integer; /* The integer when type is REDIS_REPLY_INTEGER */

    int len; /* Length of string */

    char *str; /* Used for both REDIS_REPLY_ERROR and REDIS_REPLY_STRING */

    size_t elements; /* number of elements, for REDIS_REPLY_ARRAY */

    struct redisReply **element; /* elements vector for REDIS_REPLY_ARRAY */

} redisReply;

redisContext *redisConnectWithTimeout(const char *ip, int port, struct timeval tv);

void redisFree(redisContext *c);

//Issue a command to Redis, NULL if error, otherwise reply

void *redisCommand(redisContext *c, const char *format, ...);

/* Function to free the reply objects hiredis returns by default. */

void freeReplyObject(void *reply);

应用实例：

#include "hiredis/hiredis.h"

  redisContext* context = NULL;

  redisReply* reply = NULL;

  int retry = 0;

  while (retry < 5)

  {

    reply != NULL ? freeReplyObject(reply):;

    context != NULL ? redisFree(context):;

    context = redisConnect("127.0.0.1", 8600);

    if (NULL == context || context->err != 0)

    {

      cout << "connect err" << endl;

      continue;

    }

    redisReply* reply = (redisReply*)redisCommand(context, "%s", "set name John");

    if (NULL == reply || reply == REDIS_REPLY_ERROR)

    {

     cout << "exe command fail" << endl;

     continue;

    }

    cout << "ok" << endl;

  }

  reply != NULL ? freeReplyObject(reply):;

  context != NULL ? redisFree(context):;