JSON requests in C using libcurl

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I'm defining a PUT request with a JSON request body using libcurl in C.

This how I'm doing it:

    sprintf(jsonObj, "\"name\" : \"%s\", \"age\" : \"%s\"", name, age);

    struct curl_slist *headers = NULL;
    curl_slist_append(headers, "Accept: application/json");
    curl_slist_append(headers, "Content-Type: application/json");
    curl_slist_append(headers, "charset: utf-8");

    curl_easy_setopt(curl, CURLOPT_URL, url);

    curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "PUT");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers); 
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, jsonObj);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);
    curl_easy_setopt(curl, CURLOPT_USERAGENT, "libcrp/0.1");

    res = curl_easy_perform(curl);

The request body is arriving like this:

    { '"name" : "Pedro", "age" : "22"' }

With { ' at the start and ' } at the end.

--- MORE INFO -----

if I declare this code

    char* jsonObj = "{ \"name\" : \"Pedro\" , \"age\" : \"22\" }"; 

    struct curl_slist *headers = NULL;
    curl_slist_append(headers, "Accept: application/json");
    curl_slist_append(headers, "Content-Type: application/json");
    curl_slist_append(headers, "charset: utf-8");

    curl_easy_setopt(curl, CURLOPT_URL, url);

    curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "PUT");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers); 
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, jsonObj);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);
    curl_easy_setopt(curl, CURLOPT_USERAGENT, "libcrp/0.1");

    res = curl_easy_perform(curl);

the server receives this as the request body:

{ '{ "name" : "Pedro" , "age" : "22" }': '' }

My question is:

Is the libCurl pre-formatting/encoding automatically the Json request?

By the way, does the libCurl have some way of encoding a JSON object?

Thanks so much!

libcurl c json
7 Answers

Had this same problem when posting data to node-red with json parser.
Solution for me was to treat string as a HTML

#include <curl/curl.h>

int main (int argc, char *argv[]) {
    CURL *curl;
    CURLcode res;

    curl_global_init(CURL_GLOBAL_ALL);
    curl = curl_easy_init();
    if (curl == NULL) {
        return 128;
    }
    struct curl_slist *headers = NULL;
    curl_slist_append(headers, "Content-Type: application/json");
    curl_easy_setopt(curl, CURLOPT_URL, #yourURL);
    curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "POST");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, "age=42&sex=male");

    res = curl_easy_perform(curl);

    curl_easy_cleanup(curl);
    curl_global_cleanup();
    return res;
}

Hope someone will find it helpful.

user_120525090
user_58212110
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