Upload a file using c++ via curl

Hi @hb_,

Definitely the problem is not in cited code line. Did you set properly CURLOPT_XOAUTH2_BEARER parameter? :thinking:

Hope this gives some direction.

@Здравко Thank you. You were right, I guess this time I set CURLOPT_XOAUTH2_BEARER parameter properly so it gave another error:

"Error in call to API function "files/upload": Must provide HTTP header "Authorization" or URL parameter "authorization"."

I am searching to find out what this error could be about.

If you can help in any way I would much appreciate.

hey @Здравко I think it worked

However I came to find that the code does not do what I actually want, what it does is just creates a new file and write something you specify to it but I want to upload a local file from my computer to my dropbox account?

Any idea how can I do that?

Hey @hb_,

Seems you have some progress. Most upload operations (no restricted to Dropbox) are POST based. It would be difficult (and impractical) to encode big file's content to GET parameters! Further, every content is transferred as... content and you have to direct where this content to be placed on. The target file name could be the same as source file name (if any) or different. The choice is yours! I'm not sure where you read reference info for CURL, but curl.haxx.se is good starting point and together with Dropbox API (also SDK) documents you can do what you want. Between: libcurl is C library, not C++ (as in your thread header).

Of course would be nice if there was Dropbox C/C++ SDK. It's really curious why 'fundamental' languages C and C++ are left without proper support from Dropbox side. There are many libraries providing underlying transport support that could be used as base for Dropbox 'shell'. For example Qt, WxWidgets, Boost and many others. Of course libcurl, discussed here, is also good example. This thread could be a proposal! @Greg-DB, What you would say about?

@Здравко Thanks for helping out! I can't speak to why any particular language was or wasn't supported in an official SDK, but I'll pass this along as a feature request for an official C/C++ Dropbox SDK. I can't promise if or when that might be implemented though.

@hb_ If you're still having trouble, please share the code you have so far so we can take a look.

For reference, when uploading a file to Dropbox via the Dropbox API /2/files/upload endpoint, the data for the file you want to upload needs to be sent in the request body. For example, you might do something like this:

curl_easy_setopt(curl, CURLOPT_POSTFIELDS, "data for upload here");

To get the data you want to upload, you can use whatever local file I/O access you have to read the data from the local file.

Hi @Greg-DB , thanks for replying so quick

I followed your suggestion and tried tp use std::ifstream like this:

CURL *curl;
    CURLcode res;

    /* In windows, this will init the winsock stuff */
    curl_global_init(CURL_GLOBAL_ALL);

    /* get a curl handle */
    curl = curl_easy_init();

    string test = "D:\\Desktop\\test.txt";

    std::ifstream file(test);

    if(curl)
    {
        printf ("Running curl test.\n");

        struct curl_slist *headers=NULL; /* init to NULL is important */
        headers = curl_slist_append(headers, "Authorization: Bearer <my_access_token>");
        headers = curl_slist_append(headers, "Content-Type: application/octet-stream");
        headers = curl_slist_append(headers, "Dropbox-API-Arg: {\"path\":\"/test.txt\"}");
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

        curl_easy_setopt(curl, CURLOPT_URL, "https://content.dropboxapi.com/2/files/upload");
        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, file);

        curl_easy_setopt (curl, CURLOPT_SSL_VERIFYPEER, FALSE);

        /* Perform the request, res will get the return code */
        res = curl_easy_perform(curl);
        /* Check for errors */
        if(res != CURLE_OK)
            fprintf(stderr, "curl_easy_perform() failed: %s\n",
                    curl_easy_strerror(res));

        /* always cleanup */
        curl_easy_cleanup(curl);

        printf ("\nFinished curl test.\n");

    }
    curl_global_cleanup();

    printf ("Done!\n");

but it didn't compile displaying this error:

C:\Min.GW\curl-7.64.1-win64-mingw\include\curl\curl.h|2857|error: use of deleted function 'std::basic_ifstream<_CharT, _Traits>::basic_ifstream(const std::basic_ifstream<_CharT, _Traits>&) [with _CharT = char; _Traits = std::char_traits<char>]'|

But before that I had this code:

CURL *curl;
    CURLcode res;

    /* In windows, this will init the winsock stuff */
    curl_global_init(CURL_GLOBAL_ALL);

    /* get a curl handle */
    curl = curl_easy_init();


    if(curl)
    {
        printf ("Running curl test.\n");

        struct curl_slist *headers=NULL; /* init to NULL is important */
        headers = curl_slist_append(headers, "Authorization: Bearer <my_access_token>");
        headers = curl_slist_append(headers, "Content-Type: application/octet-stream");
        headers = curl_slist_append(headers, "Dropbox-API-Arg: {\"path\":\"/D:\\Desktop\\test.txt\"}");
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

        curl_easy_setopt(curl, CURLOPT_URL, "https://content.dropboxapi.com/2/files/upload");


        curl_easy_setopt (curl, CURLOPT_SSL_VERIFYPEER, FALSE);

        /* Perform the request, res will get the return code */
        res = curl_easy_perform(curl);
        /* Check for errors */
        if(res != CURLE_OK)
            fprintf(stderr, "curl_easy_perform() failed: %s\n",
                    curl_easy_strerror(res));

        /* always cleanup */
        curl_easy_cleanup(curl);

        printf ("\nFinished curl test.\n");

    }
    curl_global_cleanup();

    printf ("Done!\n");

And this would just create new folders and files in my account
Don't know if the codes I posted might be too long, the difference between the two is only at this line:

curl_easy_setopt(curl, CURLOPT_POSTFIELDS, "test data for upload");

It's error to pass ifstream object as char sequence! You have to read the file content.

@Здравко yeah

you are right I can read a text file content into a char and pass it as a parameter but what aboout a audio file or a video?

The same. In addition you can use CURLOPT_POSTFIELDSIZE (you can't rely on zero termination).

Good example could be foud here.

@Здравко I have spent some trying to figure the code out and I did, not everything though, but I couldn't apply it to my code. It looks like it is the hard way to do that

@Greg-DB any clue?

@hb_ Yes definitely. You are trying to implement something like new SDK, in fact. That's why I proposed this on the thread! To be more easy, at least for future. May be an easier way would be take a look on some existing SDK (on language familiar to you) and reimplement what's there (at least needed parts).

@Здравко so you are saying that currently there's no way to upload file from my computer to my dropbox account using c++ via curl??

No! Just opposite. Just some more work would be needed, because of missing SDK ready. And Between: again libcurl is C library, not C++, that's why ifstream object can't be 'stream' (i.e. cast) directly. Be careful.

C code still works on C++, so any C code that can do what I am intending to do would be useful to me.

And I need to know that 'some more work' so I can do it

Yes, of course. But there are some differences you have to be aware! In C++ you can use overload functions (for example), but not in C. Again, just be careful.

I have some basic knowledge of C and I am aware of the C limitations

I really thank you @Здравко for investing so much time trying to help me. I really appreciate it.

I will keep looking for a way to do what I want.
Hopefully @Greg-DB will come with a solution

You're on the right track. That is, you can upload files to Dropbox using HTTPS requests to /2/files/upload, and you have the basic code to do so already.

It sounds like you're currently working on how to get the data from the local file system though, which isn't specific to Dropbox, so I'm afraid I can't offer much specific help with that in particular, nor do I have a code sample for that in particular. (I'm also certainly not a C expert.)

https://github.com/rahuliyer/dropbox-cpp

As I said, I will keep looking

Thank you for your time @Greg-DB

As for DropBox I will be expecting an official C++ SDK soon

Edit: As a note I found a repo on github, a dropbox api c++ library that on looks seems to do what I want but I haven't figure the whole code out and get it to work

@Здравко @Greg-DB if you guys could check it out some time and try to figure the code out and hit me back that would be awsome nit only for me but for anyone that wants to do what I want to do

Just to be clear, I've sent this along as a feature request, but I can't promise if or when Dropbox would release an official C++ SDK for API v2. (I'm not currently of any such work on one.)

I know, I just hope Dropbox releases it not in a distant future

Hi @hb_,

The code you find out seems pretty old (last update 6 years ago). Old Dropbox API is implemented there (currently deprecated, although available still). I'm not sure if there is schedule for this API support dropping. From other view point this is good example of Boost library usage (very powerful C++ library). I have no idea, in this context, why libcurl is still used (everything could be done using Boost only). Also this code could be used as good (not the best, but...) example of mixing C and C++ code. May be this could be used as start point for implementing Dropbox API v2. (at least some tips)

Good luck.

I just took a look at that third party libray, and I can confirm it does use the old Dropbox API v1. To clarify one point, Dropbox API v1 is already retired, and so it not available. Attempting Dropbox API v1 calls will fail.