Ah, right.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>

struct MemoryStruct {
    char *memory;
    size_t size;
};

size_t WriteMemoryCallback(void *contents, size_t size, size_t nmemb, struct MemoryStruct *userp) {
    size_t realsize = size * nmemb;
    userp->memory = realloc(userp->memory, userp->size + realsize + 1);
    if(userp->memory == NULL) {
        return 0;
    }
    memcpy(&(userp->memory[userp->size]), contents, realsize);
    userp->size += realsize;
    userp->memory[userp->size] = 0;
    return realsize;
}

int main(int argc, char *argv[]) {
    CURLcode ret;
    CURL *hnd;
    struct MemoryStruct chunk;

    chunk.memory = malloc(1);
    chunk.size = 0;

    hnd = curl_easy_init();
    if(hnd) {
        curl_easy_setopt(hnd, CURLOPT_BUFFERSIZE, 102400L);
        curl_easy_setopt(hnd, CURLOPT_URL, "https://pastebin.com/api/api_post.php");
        curl_easy_setopt(hnd, CURLOPT_NOPROGRESS, 1L);
        curl_easy_setopt(hnd, CURLOPT_POSTFIELDS, "api_dev_key=API_KEY_HERE&api_paste_code=test&api_option=paste");
        curl_easy_setopt(hnd, CURLOPT_POSTFIELDSIZE_LARGE, (curl_off_t)81);
        curl_easy_setopt(hnd, CURLOPT_USERAGENT, "curl/8.9.1");
        curl_easy_setopt(hnd, CURLOPT_MAXREDIRS, 50L);
        curl_easy_setopt(hnd, CURLOPT_CUSTOMREQUEST, "POST");
        curl_easy_setopt(hnd, CURLOPT_FTP_SKIP_PASV_IP, 1L);
        curl_easy_setopt(hnd, CURLOPT_TCP_KEEPALIVE, 1L);
        curl_easy_setopt(hnd, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
        curl_easy_setopt(hnd, CURLOPT_WRITEDATA, (void *)&chunk);

        ret = curl_easy_perform(hnd);

        if(ret != CURLE_OK) {
            fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(ret));
        } else {
            printf("%s\n", chunk.memory);
        }

        curl_easy_cleanup(hnd);
        free(chunk.memory);
    } else {
        fprintf(stderr, "Failed to initialize CURL\n");
    }

    return (int)ret;
}

Finished it, i think. Still does "nothing"

edit: probably shouldn't include my api key with it.