需求分析：1.需要Linux c 网络编程基础，2.需要了解 http 协议3.需要天气信息相关api(可以从阿里云上购买，很便宜的！)4.需要cJSON解析库(因为获取到的天气信息一般是用cJSON封装，有的是用xml封装则需要相关解析库)cJSON下载链接:https://github.com/DaveGamble/cJSON
cJSON在线代码格式化:http://tool.oschina.net/codeformat/json

cJSON简解及使用:cJSON核心结构体：
typedef struct cJSON
{struct cJSON *next;struct cJSON *prev;struct cJSON *child;int type;           /*键类型*/char *valuestring;  /*字符串值*/int valueint;       /*整形值*/double valuedouble; /*浮点值*/ char *string;       /*键名称*/
} cJSON;说明：cJSON数据是以（键-值）形式存在。每个键对应的值都可以访问(valuestring、valueint、valuedouble）成员得到。主要用到的函数：1. CSJON_PUBLIC(cJSON*) cJSON_Parse(const char *value);用了获得根节点，2. CSJON_PUBLIC(cJSON*) cJSON_GetObjectItem(const cJSON* const object, const char *const string);用来获得根节点下的子节点，3. CSJON_PUBLIC(void) cJSON_Delete(const cJSON *item);用来释放为根节点分配的内存!

获取天气的http协议:"GET /phone-post-code-weeather?""phone_code=021 ""HTTP/1.1\r\n""Host:ali-weather.showapi.com\r\n""Authorization:APPCODE xxxxxx\r\n\r\n"解释说明："/phone-post-code-weeather"此部分对应于 path格式"Host:ali-weather.showapi.com"此部分对应于 接口域名"phone_code" 表示城市编号021为上海(记住后面要空格)"xxxxxx" 为你购买的APPCODE 这我就不填。。。
![这里写图片描述](http://img.blog.csdn.net/20170815164731926?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvQ29taW5nRmx5aW5n/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast)

相关代码:#include <netdb.h>
#include <stdbool.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <strings.h>#include "common.h"
#include "cJSON.h"#define SERV_PORT   80typedef struct sockaddr SA;void http_request(char *buf, int size, char *city_name);
void analyze_CJSON(const char *json);
char *recv_msg(int sockfd);int main(int argc, char **argv)
{int sockfd;struct hostent *hptr = NULL;struct sockaddr_in servaddr; struct in_addr  **pptr;if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {err_quit("socket error");}char *alias_name = "ali-weather.showapi.com";//char *alias_name = "jisutianqi.market.alicloudapi.com";//得到接口域名的IP地址if ((hptr = gethostbyname(alias_name)) == NULL) {err_quit("gethostbyname error for host: %s: %s", alias_name, hstrerror(h_errno));}pptr = (struct in_addr **)hptr->h_addr_list;bzero(&servaddr, sizeof(servaddr));servaddr.sin_family  =   AF_INET;servaddr.sin_port    =   htons(SERV_PORT);memcpy(&servaddr.sin_addr, *pptr, sizeof(struct in_addr));if (connect(sockfd, (SA *)&servaddr, sizeof(servaddr)) < 0) {err_quit("connect error");}char buf[MAXLINE];//设置想要查询的城市编号，也可以安其他方式查询char *phone_code = "021";http_request(buf, MAXLINE, phone_code);//发送http请求if (write(sockfd, buf, strlen(buf)) != strlen(buf)) {err_quit("write error");}//接收返回信息char *json = recv_msg(sockfd);//解析CJSON数据analyze_CJSON(json);return EXIT_SUCCESS;
}void http_request(char *buf, int size, char *phone_code)
{bzero(buf, size);snprintf(buf, size, "GET /phone-post-code-weeather?""phone_code=%s ""HTTP/1.1\r\n"//"Host:jisutianqi.market.alicloudapi.com\r\n""Host:ali-weather.showapi.com\r\n""Authorization:APPCODE d487d937315848af80710a06f4592fee\r\n\r\n", phone_code);
}/***注意：返回的信息包含http报头信息和实际的CJSON数据，我们只*需要CJSON数据,所有需要做一定处理。**/
char * recv_msg(int sockfd)
{int nread;char recvbuf[4096];char *begin = NULL, *end = NULL;char *lenght = NULL;char *data = NULL;char tar[] = "Content-Length: ";bool flage = true;while (1) {bzero(recvbuf, sizeof(recvbuf));if ((nread = read(sockfd, recvbuf, sizeof(recvbuf))) == 0) {break;}//获得cJSON数据的字节数，存储到lenght中，并调用atoi函数将其转化为int类型if (strstr(recvbuf, "403") != NULL || strstr(recvbuf, "Quota Exhausted")) {err_quit("your appcode is expire..");}if (flage) {if ((begin = strstr(recvbuf, tar)) != NULL) {if ((end = strstr(begin, "\r\n")) != NULL) {lenght = malloc(end - (begin+strlen(tar)));memcpy(lenght, begin+strlen(tar), end-(begin+strlen(tar)));data = calloc(1, atoi(lenght));if (data == NULL) {err_quit("malloc error");}strcpy(data, strrchr(recvbuf, '\n')+1);}} else {continue;}}if (!flage) {strcat(data, recvbuf);}if (strlen(data) == atoi(lenght)) {break;}flage = false;}printf("atoi(lenght) = %d\n", atoi(lenght));free(lenght);return data;
}void analyze_CJSON(const char *json)
{//获得根节点cJSON *root = cJSON_Parse(json);if (root == NULL) {err_quit("cJSON_Parse error");}cJSON *body = cJSON_GetObjectItem(root, "showapi_res_body");if (body == NULL) {err_quit("body error");}//判断是否成功得到数据if (cJSON_GetObjectItem(body, "ret_code")->valueint == -1) {err_quit("json data invalid..");}cJSON *now = cJSON_GetObjectItem(body, "now");if (now == NULL) {err_quit("get now failure");}cJSON *aqiDetai = cJSON_GetObjectItem(now, "aqiDetail");if (aqiDetai == NULL) {err_quit("get aqiDetai failure");}cJSON *cityinfo = cJSON_GetObjectItem(body, "cityInfo");if (cityinfo == NULL) {err_quit("get cityinfo failure");}cJSON *f1 = cJSON_GetObjectItem(body, "f1");if (f1 == NULL) {err_quit("get f1 failure");}cJSON *f2 = cJSON_GetObjectItem(body, "f2");if (f1 == NULL) {err_quit("get f2 failure");}cJSON *f3 = cJSON_GetObjectItem(body, "f3");if (f1 == NULL) {err_quit("get f3 failure");}printf("            country:\t%s\n", cJSON_GetObjectItem(cityinfo, "c9")->valuestring);printf("               area:\t%s\n", cJSON_GetObjectItem(aqiDetai, "area")->valuestring);printf("            quality:\t%s\n", cJSON_GetObjectItem(aqiDetai, "quality")->valuestring);printf("              pm2_5:\t%s\n", cJSON_GetObjectItem(aqiDetai, "pm2_5")->valuestring);printf("               pm10:\t%s\n", cJSON_GetObjectItem(aqiDetai, "pm10")->valuestring);printf("                aqi:\t%s\n", cJSON_GetObjectItem(aqiDetai, "aqi")->valuestring);printf("\ntoday weather:\n");printf("        day_weather:\t%s\n", cJSON_GetObjectItem(f1, "day_weather")->valuestring);printf("     day_wind_power:\t%s\n", cJSON_GetObjectItem(f1, "day_wind_power")->valuestring);printf(" day_wind_direction:\t%s\n", cJSON_GetObjectItem(f1, "day_wind_direction")->valuestring);printf("day_air_temperature:\t%s\n", cJSON_GetObjectItem(f1, "day_air_temperature")->valuestring);printf("\ntomorrow weather:\n");printf("        day_weather:\t%s\n", cJSON_GetObjectItem(f2, "day_weather")->valuestring);printf("     day_wind_power:\t%s\n", cJSON_GetObjectItem(f2, "day_wind_power")->valuestring);printf(" day_wind_direction:\t%s\n", cJSON_GetObjectItem(f2, "day_wind_direction")->valuestring);printf("day_air_temperature:\t%s\n", cJSON_GetObjectItem(f2, "day_air_temperature")->valuestring);printf("\nthe day after tomorrow weather:\n");printf("        day_weather:\t%s\n", cJSON_GetObjectItem(f3, "day_weather")->valuestring);printf("     day_wind_power:\t%s\n", cJSON_GetObjectItem(f3, "day_wind_power")->valuestring);printf(" day_wind_direction:\t%s\n", cJSON_GetObjectItem(f3, "day_wind_direction")->valuestring);printf("day_air_temperature:\t%s\n", cJSON_GetObjectItem(f3, "day_air_temperature")->valuestring);cJSON_Delete(root);
}