libcurl下载文件的代码示例

C++中使用libcurl下载文件示例

备注：简单示例，仅供参考，个人c++

//
// sudo apt-get remove libcurl4
// sudo apt-get install libcurl4-openssl-dev
//
// g++ curl_file.cpp -std=c++11 -lcurl -o a.out;./a.out


#include 
#include 
#include 

//判断url是否存在
int checkUrlIsExist(const char * URL) {

    CURL * curl_fd = curl_easy_init();
    CURLcode code;
    CURLINFO response_code = CURLINFO_NONE;
    curl_easy_setopt(curl_fd, CURLOPT_NOBODY, 1);
    curl_easy_setopt(curl_fd, CURLOPT_TIMEOUT, 3);
    curl_easy_setopt(curl_fd, CURLOPT_URL, URL);
    code = curl_easy_perform(curl_fd);

    if (code == CURLE_OK) {
        curl_easy_getinfo(curl_fd, CURLINFO_RESPONSE_CODE, &response_code);
    }

    curl_easy_cleanup(curl_fd);

    return response_code;
}


size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream) {
    size_t written = fwrite(ptr, size, nmemb, stream);
    // prints as unsigned decimal
    printf("file writen byte:%zun", written);
    return written;
}

int main()
{
    std::string url = "https://www.jianshu.com";
    const char *cUrl = url.c_str();
    int statusCode = checkUrlIsExist(cUrl);
    if (statusCode == 404) {
        printf("url does not existn");
    } else {
        printf("statusCode:%dn", statusCode);
    }

    CURL *curl;
    FILE *fp;
    CURLcode res;

    char outfilename[FILENAME_MAX] = "./index.html";
    curl = curl_easy_init();
    if (curl) {
        fp = fopen(outfilename,"wb");
        curl_easy_setopt(curl, CURLOPT_URL, cUrl);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
        res = curl_easy_perform(curl);
        
        curl_easy_cleanup(curl);
        fclose(fp);
    }

    printf("donen");
    return 0;
}

g++ curl_file.cpp -std=c++11 -lcurl -o b.out;./b.out
结果如下
statusCode:200
file writen byte:7801
file writen byte:4096
file writen byte:3906
file writen byte:8304
done

文件写入到了index.html