在C / C使用libcurl的下载文件++ [英] Download file using libcurl in C/C++

问题描述

我建立一个应用程序（使用开发 - C ++窗口），我希望它下载文件。我做这个用的libcurl（我已经安装了源$ C ​​$ c。使用帕克曼）。我发现了一个工作示例（<一个href=\"http://siddhantahuja.word$p$pss.com/2009/04/12/how-to-download-a-file-from-a-url-and-save-onto-local-directory-in-c-using-libcurl/\">http://siddhantahuja.word$p$pss.com/2009/04/12/how-to-download-a-file-from-a-url-and-save-onto-local-directory-in-c-using-libcurl/)但下载完成后，它并没有关闭该文件。我想有人就如何下载文件为例，无论是在C或C ++。在此先感谢！

I am building an application (on windows using Dev-C++) and I want it to download a file. I am doing this using libcurl (I have already installed the source code using packman). I found a working example (http://siddhantahuja.wordpress.com/2009/04/12/how-to-download-a-file-from-a-url-and-save-onto-local-directory-in-c-using-libcurl/) but it doesn't close the file after download is complete. I would like someone to give an example on how to download a file, either in c or c++. Thanks in advance!

推荐答案

您正在使用的例子是错误的。请参阅 easy_setopt 手册页。在这个例子中WRITE_DATA使用自己的文件，* OUTFILE，而不是在CURLOPT_WRITEDATA指定的FP。这就是为什么收盘FP造成问题 - 它甚至没有打开

The example you are using is wrong. See the man page for easy_setopt. In the example write_data uses its own FILE, *outfile, and not the fp that was specified in CURLOPT_WRITEDATA. That's why closing fp causes problems - it's not even opened.

这或多或少是它应该是什么样子（可在这里进行测试没有的libcurl）

This is more or less what it should look like (no libcurl available here to test)

#include <stdio.h>
#include <curl/curl.h>
/* For older cURL versions you will also need 
#include <curl/types.h>
#include <curl/easy.h>
*/
#include <string>

size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream) {
    size_t written = fwrite(ptr, size, nmemb, stream);
    return written;
}

int main(void) {
    CURL *curl;
    FILE *fp;
    CURLcode res;
    char *url = "http://localhost/aaa.txt";
    char outfilename[FILENAME_MAX] = "C:\\bbb.txt";
    curl = curl_easy_init();
    if (curl) {
        fp = fopen(outfilename,"wb");
        curl_easy_setopt(curl, CURLOPT_URL, url);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
        res = curl_easy_perform(curl);
        /* always cleanup */
        curl_easy_cleanup(curl);
        fclose(fp);
    }
    return 0;
}

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更新：通过@rsethc types.h中和 easy.h 不是present的建议当前版本的卷曲了。

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Updated: as suggested by @rsethc types.h and easy.h aren't present in current cURL versions anymore.

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