Code example of libcurl download file

C++ Use in libcurl Download sample files

remarks ： A simple example , For reference only , personal c++

Code

//
// 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 <iostream>
#include <stdlib.h>
#include <curl/curl.h>

// Judge url Whether there is 
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:%zu\n", 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 exist\n");
    } else {
    
        printf("statusCode:%d\n", 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);
        /* always cleanup */
        curl_easy_cleanup(curl);
        fclose(fp);
    }

    printf("done\n");
    return 0;
}

Execute the following command

g++ curl_file.cpp -std=c++11 -lcurl -o b.out;./b.out
give the result as follows
statusCode:200
file writen byte:7801
file writen byte:4096
file writen byte:3906
file writen byte:8304
done

The file is written to index.html