Question

我正在尝试从服务器上下载.txt文件，我可以通过树莓派上的网络浏览器访问该文件。

当我尝试这样做时，Curl库给出了细分错误。这是我正在使用的代码。

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 checkNewFiles(){
    CURL *curl;
    FILE *fp;
    CURLcode res;
    string url = "http://52.233.176.151:1880/files/device/software/text.txt";
    char outfilename[FILENAME_MAX] = "/home/pi/Desktop/project/cpp/ab.txt";
    curl = curl_easy_init();
    if (curl) {
        fp = fopen(outfilename, "wb");
        curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
        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);
      }
    return 0;
}

Answer 1

我发现了问题，url.c_str()在做什么？

curl_easy_setopt(curl, CURLOPT_URL, url.c_str());

将此更改为

curl_easy_setopt(curl, CURLOPT_URL, url);

示例：下载文本文件的Curl程序。

当然，您需要在此处添加此必要的头文件。

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;
    const char *url = "http://localhost/yourfile.txt";
    char outfilename[FILENAME_MAX] = "C:\\outfile.txt";
    curl = curl_easy_init();
    if (curl) {
        fp = fopen(outfilename,"wb");
        curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1); /* enable failure on http errors */
        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);
        if(res != CURLE_OK) { /* check that the operation was successful */
          printf("curl_easy_perform(): %s\n", curl_easy_strerror(res));
        }
        /* always cleanup */
        curl_easy_cleanup(curl);
        fclose(fp);
    }
    return 0;
}

Answer 2

我注意到您在fopen之后没有检查错误。如果失败，它将返回一个NULL指针，在curl尝试对其进行写操作时将导致段错误。

我不相信c_str()是原始问题中段错误的罪魁祸首，因为我已经在很多应用程序中毫无问题地使用了它。

卷毛给出分段错误错误

2 个答案: