Elasticsearch可以通过http报文和json语句来进行增删查改，可以通过libcurl构造语句，去发送到es集群进行操作。参考
https://blog.csdn.net/xsdxs/article/details/72849796
https://stackoverflow.com/questions/25887453/how-to-use-libcurl-in-c-to-send-post-to-elasticsearch
实现一个简便的esclient（）函数，方便读写
运行结果：
图1是查询单条语句的结果
图2是批量查询的结果
图3是以上程序运行前的图
图4是以上程序运行后的图
附录：以上源码
```
#include
#include
#include
#include
#include
using namespace std;
size_t write_data(void *ptr, size_t size, size_t nmemb, void *stream)
{
strncat((char *)stream, (char *)ptr, size*nmemb);
return size * nmemb;
}
int esclient(const string &_http, const string &_json, const string &_command)
{
CURL *curl;
CURLcode res;
struct curl_slist* headers = NULL;
curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);
curl_easy_setopt(curl, CURLOPT_URL, _http.c_str());
headers=curl_slist_append(headers, "Content-Type:application/json");
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
char out[40960]={0};
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &out);
if(_command=="delete")
{
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "DELETE");
}
else if(_command=="get")
{
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "GET");
}
else
{
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "POST");
}
if(!_json.empty())
{
curl_easy_setopt(curl,CURLOPT_POSTFIELDS,_json.c_str());
curl_easy_setopt(curl,CURLOPT_POSTFIELDSIZE,_json.length());
}
res = curl_easy_perform(curl);
printf("%s\n",out);
curl_easy_cleanup(curl);
return res;
}
int main(void)
{
esclient("http://172.31.100.114:9200/customer/external/1","","get"); //查询单条数据
esclient("http://172.31.100.114:9200/bank/_search","","search"); //批量查询数据，但是只返回10条，如需其他要求，加json语句
esclient("http://172.31.100.114:9200/customer/external/3/"," { \"name\": \"hhh\" }","add"); //增加一条数据
esclient("http://172.31.100.114:9200/customer/external/2/_updata/"," {\"doc\": { \"name\": \"eee\" }}","updata"); //更新某条数据
esclient("http://172.31.100.114:9200/ccc","","delete"); //删除索引
esclient("http://172.31.100.114:9200/customer/external/_delete_by_query"," {\"query\":{ \"match\":{\"name\": \"hhh\" }}}",""); //匹配删除数据
}
```
