Download file using libcurl in C/C++ - c

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 an example of how to download a file in C.

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

Just for those interested you can avoid writing custom function by passing NULL as last parameter (if you do not intend to do extra processing of returned data).
In this case default internal function is used.
Details
http://curl.haxx.se/libcurl/c/curl_easy_setopt.html#CURLOPTWRITEDATA
Example
#include <stdio.h>
#include <curl/curl.h>
int main(void)
{
CURL *curl;
FILE *fp;
CURLcode res;
char *url = "http://stackoverflow.com";
char outfilename[FILENAME_MAX] = "page.html";
curl = curl_easy_init();
if (curl)
{
fp = fopen(outfilename,"wb");
curl_easy_setopt(curl, CURLOPT_URL, url);
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, NULL);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
fclose(fp);
}
return 0;
}

Related

Building a file with an attached library as one file

I write simple software to download image file from specific url. I using libcurl, i have this code:
#define CURL_STATICLIB
#include <stdio.h>
#include <curl/curl.h>
size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream) {
size_t written;
written = fwrite(ptr, size, nmemb, stream);
return written;
}
int downloadFile() {
CURL *curl;
FILE *fp;
CURLcode res;
char *url = "http://www.example.eu/12.jpg";
char outfilename[FILENAME_MAX] = "D:\\12.jpg";
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);
curl_easy_cleanup(curl);
fclose(fp);
}
}
int main(void) {
downloadFile();
return 0;
}
When i build project i need copy dll file to project directory, because without him i have error. Is there any way to build an exe file with a built-in library? so to have the exe itself without having to attach another file?
I count on the fact that the file will be larger but for me it is a lot easier if I have 1 file, not a few, because as I add some files now I will have 1 exe and many dll files.

Play mp3 file in C

I want to play mp3 files on the internet without downloading them. So, I use libcurl to get it as a stream in memory, like this:
static size_t use_data(void *ptr, size_t size, size_t nmemb, FILE *stream) {
/* stream is NULL */
/* What to do with the stream of data ? */
}
CURLcode download_file(const char *url, const char *path, curl_progress_callback progress) {
CURL *curl;
CURLcode res = 0;
FILE *fp;
if ((curl = curl_easy_init())) {
if (progress) {
curl_easy_setopt(curl, CURLOPT_NOPROGRESS, 0);
curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, progress);
}
curl_easy_setopt(curl, CURLOPT_URL, url);
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, use_data);
res = curl_easy_perform(curl);
/* always cleanup */
curl_easy_cleanup(curl);
fclose(fp);
}
return res;
}
How can I parse the stream in memory to play sounds ?
The easiest way for you IMHO would be using lightweight MP3 decoding library. For example, minimp3 does it's job and consists of only 2 files.
http://keyj.emphy.de/minimp3
The API is very simple and a usage example can be found here: https://github.com/corporateshark/PortAMP/tree/master/src/Decoders/MP3

Not completed downloading of file (segmentation fault) while using curl on Ubuntu 14.04

After compiling my program i get this error:
I'm using Code::Blocks.Program is written to be easy download manager. Problem occurs with all types of files (pdf,txt,jpg). Here's my code. I don't know why is it happening. Please help.
#define CURL_STATICLIB
#include <stdio.h>
#include <curl/curl.h>
#include <string.h>
size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream)
{
size_t written;
written = fwrite(ptr, size, nmemb, stream);
return written;
}
int main(void)
{
CURL *curl;
FILE *fp;
CURLcode res;
int x;
char y[200];
char page;
char* outfilename;
char* path_pdf = "/home/user/Desktop/document.pdf";
char* path_jpg = "/home/user/Desktop/picture.jpg";
char* path_txt = "/home/user/Desktop/document.txt";
char FILEPATH[3] = {path_pdf, path_jpg, path_txt};
printf("Enter file url: \n"); // for example http://oi58.tinypic.com/15nk3de.jpg
scanf ("%s",y);
char *url = y;
printf("Choose type of file:\n [0] - pdf\n [1] - jpg\n [2] - txt\n "); //choose 1
scanf("%d",&x);
outfilename = FILEPATH[x];
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);
curl_easy_setopt (curl, CURLOPT_VERBOSE, 1L);
res = curl_easy_perform(curl);
if (res == CURLE_OK)
{
printf("File downloaded!\n");
}
curl_easy_cleanup(curl);
fclose(fp);
}
return 0;
}
char FILEPATH[3] = {path_pdf, path_jpg, path_txt};
Is an array of char's (you want an array of strings), change to:
char *FILEPATH[3] = {path_pdf, path_jpg, path_txt};

How to download a ZIP file from server using cURL in C?

I am developing on Linux platform. I am using libcurl and able to receive json response and saving it to file. Below is the code.
#include <curl/curl.h>
#include <curl/types.h>
#include <curl/easy.h>
#include <string.h>
#define URL "http://www.joes-hardware.com/tools.html"
size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream) {
size_t written;
written = fwrite(ptr, size, nmemb, stream);
return written;
}
int main(void) {
CURL *curl;
FILE *fp;
CURLcode res;
//const char url[] = "http://www.joes-hardware.com/tools.html";
char *url= URL;
char outfilename[FILENAME_MAX] = "./json";
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);
curl_easy_cleanup(curl);
fclose(fp);
}
return 0;
}
Now I need to fetch a zip file from the server. Suppose the URL is of the format shown below:
#define URL "https://Server/File.zip"
For such URL, the code is not able to save the zip file.
How to achieve this?
I resolved the issue. The problem was with HTTPS connection. I had to add certificates for HTTPS.
Based on below links:
Can't connect to HTTPS site using cURL. Returns 0 length content instead
Getting no content from a HTTPS connection using CURL
#define CURL_STATICLIB
#include <stdio.h>
#include <curl/curl.h>
#include <curl/types.h>
#include <curl/easy.h>
#include <string.h>
#include <stdlib.h>
#define false 0
size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream) {
size_t written;
written = fwrite(ptr, size, nmemb, stream);
return written;
}
int main(void) {
CURL *curl;
FILE *fp;
CURLcode res;
const char url[] = "https://example.com/filename.zip";
const char outfilename[FILENAME_MAX] = "./json.zip";
curl_version_info_data * vinfo = curl_version_info(CURLVERSION_NOW);
if(vinfo->features & CURL_VERSION_SSL){
printf("CURL: SSL enabled\n");
}else{
printf("CURL: SSL not enabled\n");
}
curl = curl_easy_init();
if (curl) {
fp = fopen(outfilename,"wb");
/* Setup the https:// verification options. Note we */
/* do this on all requests as there may be a redirect */
/* from http to https and we still want to verify */
curl_easy_setopt(curl, CURLOPT_URL, url);
curl_easy_setopt(curl, CURLOPT_CAINFO, "./ca-bundle.crt");
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, false);
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, false);
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
int i=fclose(fp);
if( i==0)
system("unzip -j json.zip");
}
return 0;
}

the downloaded file is not saving in given location

#define CURL_STATICLIB
#include <stdio.h>
#include <curl/curl.h>
#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;
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);
curl_easy_cleanup(curl);
fclose(fp);
}
return 0;
}
Some one has posted this code for a question. But on execution of this file the downloaded file is not saving in C drive rather a new txt file will be generating with name "C:\cat.txt"... I want the downloaded file will be stored in my desired location in hard drive.. can any one help me...
First, the default CURLOPT_WRITEFUNCTION accepts a FILE * and uses fwrite using whatever's been set with CURLOPT_WRITEDATA, so you don't need to override the function unless you're using curl as a Win32 DLL.
Also, you aren't checking the return from fopen, which may fail.
I suspect in this case that you either aren't recompiling your code, or are running a different binary from the one you built

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