curl

curl是一个利用URL语法在命令行下工作的文件传输工具，1997年首次发行。它支持文件上传和下载，所以是综合传输工具，但按传统，习惯称cURL为下载工具。cURL还包含了用于程序开发的libcurl。cURL支持的通信协议有FTP、FTPS、HTTP、HTTPS、TFTP、SFTP、Gopher、SCP、Telnet、DICT、FILE、LDAP、LDAPS、IMAP、POP3、SMTP和RTSP。curl还支持SSL认证、HTTP POST、HTTP PUT、FTP上传, HTTP form based upload、proxies、HTTP/2、cookies、用户名+密码认证(Basic, Plain, Digest, CRAM-MD5, NTLM, Negotiate and Kerberos)、file transfer resume、proxy tunneling。更具体的说明包括示例请移步社区链接。

社区链接

curl 官网：https://curl.haxx.se/
book：https://bookcurl.haxx.se

安装curl

个人电脑是ubuntu系统，命令安装即可，其他系统没试过。当然也可以下载安装包进行安装。

sudo apt-get install libcurl-openssl-dev

post示例

#include <curl/curl.h>
#include <string.h>
#include <iostream>
#include <opencv2/highgui/highgui.hpp>struct MemoryStruct {char *memory;size_t size;
};size_t WriteMemoryCallback(void *contents, size_t size, size_t nmemb,void *userp) {size_t realsize = size * nmemb;struct MemoryStruct *mem = (struct MemoryStruct *)userp;mem->memory = (char *)realloc(mem->memory, mem->size + realsize + 1);if (mem->memory == NULL) {/* out of memory! */printf("not enough memory (realloc returned NULL)\n");return 0;}memcpy(&(mem->memory[mem->size]), contents, realsize);mem->size += realsize;mem->memory[mem->size] = 0;userp = mem;return realsize;
}int add_image() {CURL *curl;cJSON *post_json = cJSON_CreateObject();if (!post_json) {return false;}cJSON_AddStringToObject(post_json, "img_id", "test");std::string post_data = cJSON_PrintUnformatted(post_json);cJSON_Delete(post_json);printf("%s\n", post_data.c_str());curl = curl_easy_init();/* initialize custom header list (stating that Expect: 100-continue is notwanted */headerlist = curl_slist_append(headerlist, "Expect:");if (curl) {/* what URL that receives this POST */curl_easy_setopt(curl, CURLOPT_URL, "http://192.168.1.2:80/image");// curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist);curl_easy_setopt(curl, CURLOPT_POSTFIELDS, post_data.c_str());struct MemoryStruct chunk;chunk.memory = (char *)malloc(1); if (NULL == chunk.memory) {curl_slist_free_all(headerlist);curl_formfree(formpost);curl_easy_cleanup(curl);return false;}chunk.size = 0;curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);CURLcode res = curl_easy_perform(curl);printf("--> res: %d\n", res);printf("--> %s\n", chunk.memory);/* always cleanup */curl_easy_cleanup(curl);/* then cleanup the formpost chain */curl_formfree(formpost);/* free slist */curl_slist_free_all(headerlist);free(chunk.memory);}return 0;
}

postform示例 - file

#include <curl/curl.h>
#include <string.h>
#include <iostream>
#include <opencv2/highgui/highgui.hpp>struct MemoryStruct {char *memory;size_t size;
};size_t WriteMemoryCallback(void *contents, size_t size, size_t nmemb,void *userp) {size_t realsize = size * nmemb;struct MemoryStruct *mem = (struct MemoryStruct *)userp;mem->memory = (char *)realloc(mem->memory, mem->size + realsize + 1);if (mem->memory == NULL) {/* out of memory! */printf("not enough memory (realloc returned NULL)\n");return 0;}memcpy(&(mem->memory[mem->size]), contents, realsize);mem->size += realsize;mem->memory[mem->size] = 0;userp = mem;return realsize;
}int add_image() {CURL *curl;struct curl_httppost *formpost = NULL;struct curl_httppost *lastptr = NULL;struct curl_slist *headerlist = NULL;curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "img", CURLFORM_FILE,"/home/ubuntu/Pictures/test.jpg", CURLFORM_END);curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "img_id",CURLFORM_COPYCONTENTS, "test", CURLFORM_END);curl = curl_easy_init();/* initialize custom header list (stating that Expect: 100-continue is notwanted */headerlist = curl_slist_append(headerlist, "Expect:");if (curl) {/* what URL that receives this POST */curl_easy_setopt(curl, CURLOPT_URL, "http://192.168.1.2:80/image");// curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist);curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);struct MemoryStruct chunk;chunk.memory = (char *)malloc(1); if (NULL == chunk.memory) {curl_slist_free_all(headerlist);curl_formfree(formpost);curl_easy_cleanup(curl);return false;}chunk.size = 0;curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);CURLcode res = curl_easy_perform(curl);printf("--> res: %d\n", res);printf("--> %s\n", chunk.memory);/* always cleanup */curl_easy_cleanup(curl);/* then cleanup the formpost chain */curl_formfree(formpost);/* free slist */curl_slist_free_all(headerlist);free(chunk.memory);}return 0;
}

postform示例 - buffer

#include <curl/curl.h>
#include <string.h>
#include <iostream>
#include <opencv2/highgui/highgui.hpp>
#include <vector>struct MemoryStruct {char *memory;size_t size;
};size_t WriteMemoryCallback(void *contents, size_t size, size_t nmemb,void *userp) {size_t realsize = size * nmemb;struct MemoryStruct *mem = (struct MemoryStruct *)userp;mem->memory = (char *)realloc(mem->memory, mem->size + realsize + 1);if (mem->memory == NULL) {/* out of memory! */printf("not enough memory (realloc returned NULL)\n");return 0;}memcpy(&(mem->memory[mem->size]), contents, realsize);mem->size += realsize;mem->memory[mem->size] = 0;userp = mem;return realsize;
}int add_image() {CURL *curl;struct curl_httppost *formpost = NULL;struct curl_httppost *lastptr = NULL;struct curl_slist *headerlist = NULL;char *img_buf;std::vector<unsigned char> buff;cv::Mat img = cv::imread("/home/ubuntu/Pictures/test.jpg");cv::imencode(".jpg", img, buff);img_buf = (char *)malloc(buff.size());memcpy(img_buf, &buff[0], buff.size());for (int j = 0; j < buff.size(); j++) {img_buf[j] = buff[j];}int len = buff.size();curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "img", CURLFORM_BUFFER,"data", CURLFORM_BUFFERPTR, img_buf, CURLFORM_BUFFERLENGTH, len,CURLFORM_CONTENTTYPE, "image/jpeg", CURLFORM_END);curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "img_id",CURLFORM_COPYCONTENTS, "test1", CURLFORM_END);curl = curl_easy_init();/* initialize custom header list (stating that Expect: 100-continue is notwanted */headerlist = curl_slist_append(headerlist, "Expect:");if (curl) {/* what URL that receives this POST */curl_easy_setopt(curl, CURLOPT_URL, "http://192.168.1.2:80/image");// curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist);curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);struct MemoryStruct chunk;chunk.memory = (char *)malloc(1); if (NULL == chunk.memory) {curl_slist_free_all(headerlist);curl_formfree(formpost);curl_easy_cleanup(curl);return false;}chunk.size = 0; curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);CURLcode res = curl_easy_perform(curl);printf("--> res: %d\n", res);printf("--> %s\n", chunk.memory);/* always cleanup */curl_easy_cleanup(curl);/* then cleanup the formpost chain */curl_formfree(formpost);/* free slist */curl_slist_free_all(headerlist);free(chunk.memory);}return 0;
}

end

入门快速上手贴，有问题的地方请指正。更详细的操作请移步本文社区链接。

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