使用libcurl提交POST请求

最近在学习libcurl，并利用它提交POST请求，可是返回的响应总是无从验证该次POST请求是否成功提交了。

1. 先看下根据firebug提交的一次成功的请求，这里以login我喜欢上的xiami为例，嘻嘻~

1.1 本次POST请求的HTTP交互

1.2 POST

1.3 经server端redirect的GET

2. OK，接下来看下使用libcurl向xiami发送POST请求

2.1 使用libcurl的大概流程
curl_easy_init()
curl_easy_setopt()
curl_easy_perform()
curl_easy_cleanup()
呵呵~超简单的吧，具体的意思这里就不详细说了，参见http://curl.haxx.se/libcurl/c/

2.2 再来看简单的代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>

#define POSTURL "http://www.xiami.com/member/login"
#define POSTFIELDS "email=myemail@163.com&password=mypassword&autologin=1&submit=登 录&type="
#define FILENAME "curlposttest.log"

size_t write_data(void *buffer, size_t size, size_t nmemb, void *userp);

int main(int argc, char *argv[]) {
    CURL *curl;
    CURLcode res;
    FILE *fptr;
    struct curl_slist *http_header = NULL;

    if ((fptr = fopen(FILENAME, "w")) == NULL) {
        fprintf(stderr, "fopen file error: %s
", FILENAME);
        exit(1);
    }

    curl = curl_easy_init();
    curl_easy_setopt(curl, CURLOPT_URL, POSTURL);
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, POSTFIELDS);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, fptr);
    curl_easy_setopt(curl, CURLOPT_POST, 1);
    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);
    curl_easy_setopt(curl, CURLOPT_HEADER, 1);
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1);
    curl_easy_setopt(curl, CURLOPT_COOKIEFILE, "/Users/zhu/CProjects/curlposttest.cookie");
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
}

size_t write_data(void *buffer, size_t size, size_t nmemb, void *userp) {
    FILE *fptr = (FILE*)userp;
    fwrite(buffer, size, nmemb, fptr);
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>

#define POSTURL "http://www.xiami.com/member/login"
#define POSTFIELDS "email=myemail@163.com&password=mypassword&autologin=1&submit=登 录&type="
#define FILENAME "curlposttest.log"

size_t write_data(void *buffer, size_t size, size_t nmemb, void *userp);

int main(int argc, char *argv[]) {
    CURL *curl;
    CURLcode res;
    FILE *fptr;
    struct curl_slist *http_header = NULL;

    if ((fptr = fopen(FILENAME, "w")) == NULL) {
        fprintf(stderr, "fopen file error: %s
", FILENAME);
        exit(1);
    }

    curl = curl_easy_init();
    curl_easy_setopt(curl, CURLOPT_URL, POSTURL);
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, POSTFIELDS);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, fptr);
    curl_easy_setopt(curl, CURLOPT_POST, 1);
    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);
    curl_easy_setopt(curl, CURLOPT_HEADER, 1);
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1);
    curl_easy_setopt(curl, CURLOPT_COOKIEFILE, "/Users/zhu/CProjects/curlposttest.cookie");
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
}

size_t write_data(void *buffer, size_t size, size_t nmemb, void *userp) {
    FILE *fptr = (FILE*)userp;
    fwrite(buffer, size, nmemb, fptr);
}

2.3 说下这当中的一些操作吧

CURLOPT_URL: URL地址
CURLOPT_POSTFIELDS: POST参数
CURLOPT_WRITEFUNCTION: 对返回的数据进行操作的函数地址
CURLOPT_WRITEDATA: 设置WRITEFUNCTION的第四个参数值
CURLOPT_POST: 设置为非0表示本次操作为POST
CURLOPT_VERBOSE: 设置为非0在执行时打印请求信息
CURLOPT_HEADER: 设置为非0将响应头信息同响应体一起传给WRITEFUNCTION
CURLOPT_FOLLOWLOCATION: 设置为非0，响应头信息Location

CURLOPT_COOKIEFILE: 哈哈，这个实在是太重要了，我之前尝试了好多次没法验证该次POST是否成功的原因就是没有设置这个罗。设置对应的COOKIEFILE路径，该路径文件并不一定需要在物理磁盘上实际存在

2.4 接下来是成功返回的结果哦，呵呵，下面截图当中的zhuzhu可以为证，不好意思，xiami上取了个比较CUO的名字~