C program calling OpenAI API

open_ai.c

// by modrobert in 2024

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

int main(int argc, char *argv[])
{

  if (argc != 2)
  {
    fprintf(stderr, "need a request string\n");
    return (1);
  }

  CURLcode ret;
  CURL *hnd;
  struct curl_slist *slist1;

  char req[1000] = "";
  char auth_header[200] = "";
  int len = 0;

  const char *req1 = "{\n     \"model\": \"gpt-3.5-turbo\",\n     \"messages\": [{\"role\": \"user\", \"content\": \"";
  const char *req2 = "\"}],\n     \"temperature\": 0.7\n   }";
  const char *auth_header1 = "Authorization: Bearer ";

  // read the environment variable
  const char *api_key = secure_getenv("OPENAI_API_KEY");
  if (api_key == NULL)
  {
    fprintf(stderr, "OPENAI_API_KEY environment variable not set!\n");
    return (1);
  }

  // create auth header string
  len = snprintf(auth_header, sizeof(auth_header), "%s%s", auth_header1, api_key);
  if (len < 0)
  {
    fprintf(stderr, "auth header string error!\n");
    return (1);
  }

  // create request string
  len = snprintf(req, sizeof(req), "%s%s%s", req1, argv[1], req2);
  if (len < 0)
  {
    fprintf(stderr, "request string error!\n");
    return (1);
  }

  // curl stuff
  slist1 = NULL;
  slist1 = curl_slist_append(slist1, "Content-Type: application/json");
  slist1 = curl_slist_append(slist1, auth_header);

  hnd = curl_easy_init();
  curl_easy_setopt(hnd, CURLOPT_BUFFERSIZE, 102400L);
  curl_easy_setopt(hnd, CURLOPT_URL, "https://api.openai.com/v1/chat/completions");
  curl_easy_setopt(hnd, CURLOPT_NOPROGRESS, 1L);
  curl_easy_setopt(hnd, CURLOPT_POSTFIELDS, req);
  curl_easy_setopt(hnd, CURLOPT_POSTFIELDSIZE_LARGE, (curl_off_t)len);
  curl_easy_setopt(hnd, CURLOPT_HTTPHEADER, slist1);
  curl_easy_setopt(hnd, CURLOPT_USERAGENT, "curl/7.81.0");
  curl_easy_setopt(hnd, CURLOPT_MAXREDIRS, 50L);
  curl_easy_setopt(hnd, CURLOPT_HTTP_VERSION, (long)CURL_HTTP_VERSION_2TLS);
  curl_easy_setopt(hnd, CURLOPT_FTP_SKIP_PASV_IP, 1L);
  curl_easy_setopt(hnd, CURLOPT_TCP_KEEPALIVE, 1L);

  ret = curl_easy_perform(hnd);

  curl_easy_cleanup(hnd);
  hnd = NULL;
  curl_slist_free_all(slist1);
  slist1 = NULL;

  return (int)ret;
}

The output default is JSON, to get only "raw content" do something like:

./open_ai "what is the movie vanishing point from 1971 about?" | jq -c -r ".choices[0].message.content"