24.c

/*
============================================================================
Name : 24
Author : Piyush Singh
Description : Write a program to create a message queue and print the key and message queue id.
Date: 26th Sep, 2025.
============================================================================
*/

// Program: Create a System V message queue and print key + ID
#include <stdio.h>       // For printf(), perror()
#include <stdlib.h>      // For exit()
#include <sys/ipc.h>     // For IPC_CREAT, ftok()
#include <sys/msg.h>     // For msgget()

int main() 
{
    // Step 1: Generate a unique key using ftok
    // ftok uses a filename and a project ID to generate a key
    key_t key = ftok(".", 'A');  // '.' = current dir, 'A' = project ID
    if (key == -1) 
    {
        perror("❌ ftok failed");
        exit(1);
    }

    // Step 2: Create a message queue with the generated key
    // IPC_CREAT creates the queue if it doesn't exist
    int msgid = msgget(key, IPC_CREAT | 0666);  // 0666 = read/write permissions
    if (msgid == -1) 
    {
        perror("❌ msgget failed");
        exit(1);
    }

    // Step 3: Print the key and message queue ID
    printf("🔑 Message Queue Key: %d\n", key);
    printf("🆔 Message Queue ID: %d\n", msgid);

    return 0;
}

/*
Output:
╰─ ./24                                                                       ─╯
🔑 Message Queue Key: 1091576192
🆔 Message Queue ID: 65537
*/