`luc119.c`¶

Problem Statement

Write a program to analyse a given sentence to detect the mood of the sentence using OpenAI Chat Completion API.

Metadata¶

Property	Detail
Author	Amit Dutta amitdutta4255@gmail.com
Date	08 Feb 2026
License	MIT License (See the LICENSE file for details)
Difficulty	Beginner (index: 3 / 10)

Concepts¶

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Source Code¶

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

/* Pre-requisites:
   1. Install libcurl.
   2. Get OpenAI API Key.
*/

#define API_KEY "YOUR_OPENAI_API_KEY_HERE"

int main(void) {
    CURL *curl;
    CURLcode res;

    const char *url = "https://api.openai.com/v1/chat/completions";

    /* We construct the JSON payload manually.
       System prompt instructs the model to detect mood.
       User prompt is the sentence to analyze.
    */
    const char *data = "{"
                       "\"model\": \"gpt-3.5-turbo\","
                       "\"messages\": ["
                       "  {\"role\": \"system\", \"content\": \"You are a helpful assistant. Analyze the mood of the user input sentence. Return only the mood keywords (e.g., admiration, appreciation, anger, joy).\"},"
                       "  {\"role\": \"user\", \"content\": \"I am so impressed by your performance\"}"
                       "]"
                       "}";

    struct curl_slist *headers = NULL;
    char auth_header[100];
    sprintf(auth_header, "Authorization: Bearer %s", API_KEY);

    curl = curl_easy_init();
    if(curl) {
        headers = curl_slist_append(headers, "Content-Type: application/json");
        headers = curl_slist_append(headers, auth_header);

        curl_easy_setopt(curl, CURLOPT_URL, url);
        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data);
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

        printf("Analyzing sentence: 'I am so impressed by your performance'\n");
        printf("Waiting for OpenAI response...\n\n");

        // The response will be printed to standard output
        res = curl_easy_perform(curl);

        if(res != CURLE_OK)
            fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));

        printf("\n\n(Parse the JSON above to extract the 'content' field)\n");

        curl_slist_free_all(headers);
        curl_easy_cleanup(curl);
    }
    return 0;
}

Explanation¶

Explain with AI

Copy the prompt below and paste it into any AI assistant.

    You are explaining a C programming code to a beginner.

    STRICT RULES:

    - Only use the given code. Do NOT assume anything not present.

    - Do NOT add extra examples.

    - Keep explanation clear and short.

    - If something is unclear, say "Not clear from code".

    - Follow the exact format below. Do NOT change headings.

    FORMAT:

    [START]

    ## What it does

    (Explain the overall purpose in 1-2 sentences)

    ## Step-by-step

    (Explain how the code works in steps, simple language)

    ## Key Concepts

    (List concepts like loop, condition, function, etc.)

    ## Notes

    (Mention any limitations, errors, or assumptions)

    [END]

    CODE (luc119.c):

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

    /* Pre-requisites:
       1. Install libcurl.
       2. Get OpenAI API Key.
    */

    #define API_KEY "YOUR_OPENAI_API_KEY_HERE"

    int main(void) {
        CURL *curl;
        CURLcode res;

        const char *url = "https://api.openai.com/v1/chat/completions";

        /* We construct the JSON payload manually.
           System prompt instructs the model to detect mood.
           User prompt is the sentence to analyze.
        */
        const char *data = "{"
                           "\"model\": \"gpt-3.5-turbo\","
                           "\"messages\": ["
                           "  {\"role\": \"system\", \"content\": \"You are a helpful assistant. Analyze the mood of the user input sentence. Return only the mood keywords (e.g., admiration, appreciation, anger, joy).\"},"
                           "  {\"role\": \"user\", \"content\": \"I am so impressed by your performance\"}"
                           "]"
                           "}";

        struct curl_slist *headers = NULL;
        char auth_header[100];
        sprintf(auth_header, "Authorization: Bearer %s", API_KEY);

        curl = curl_easy_init();
        if(curl) {
            headers = curl_slist_append(headers, "Content-Type: application/json");
            headers = curl_slist_append(headers, auth_header);

            curl_easy_setopt(curl, CURLOPT_URL, url);
            curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data);
            curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

            printf("Analyzing sentence: 'I am so impressed by your performance'\n");
            printf("Waiting for OpenAI response...\n\n");

            // The response will be printed to standard output
            res = curl_easy_perform(curl);

            if(res != CURLE_OK)
                fprintf(stderr, "curl_easy_perform() failed: 
    ... (truncated for brevity)

luc119.c¶