Enrico Fraccaroli
111 lines
3.4 KiB
C
111 lines
3.4 KiB
C
/// @file t_msgget.c
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/// @brief This program creates a message queue.
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/// @copyright (c) 2014-2023 This file is distributed under the MIT License.
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/// See LICENSE.md for details.
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#include "string.h"
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#include "sys/unistd.h"
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#include "sys/errno.h"
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#include "sys/msg.h"
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#include "sys/ipc.h"
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#include "stdlib.h"
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#include "fcntl.h"
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#include "stdio.h"
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#define MESSAGE_LEN 100
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// structure for message queue
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typedef struct {
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long mesg_type;
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char mesg_text[MESSAGE_LEN];
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} message_t;
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static inline void __send_message(int msqid, long mtype, message_t *message, const char *msg)
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{
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// Set the type.
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message->mesg_type = mtype;
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// Set the content.
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strncpy(message->mesg_text, msg, MESSAGE_LEN);
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// Send the message.
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if (msgsnd(msqid, message, sizeof(message->mesg_text), 0) < 0) {
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perror("Failed to send the message");
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} else {
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printf("[%2d] Message sent (%2d) `%s`\n", getpid(), message->mesg_type, message->mesg_text);
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}
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}
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static inline void __receive_message(int msqid, long mtype, message_t *message)
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{
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// Clear the user-defined message.
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memset(message->mesg_text, 0, sizeof(char) * MESSAGE_LEN);
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// Receive the message.
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if (msgrcv(msqid, message, sizeof(message->mesg_text), mtype, 0) < 0) {
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perror("Failed to receive the message");
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} else {
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printf("[%2d] Message received (%2d) `%s` (Query: %2d)\n", getpid(), message->mesg_type, message->mesg_text, mtype);
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}
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}
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int main(int argc, char *argv[])
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{
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message_t message;
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long ret;
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key_t key;
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int msqid;
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// ========================================================================
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// Generating a key using ftok
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key = ftok("/home/user/test7.txt", 5);
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if (key < 0) {
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perror("Failed to generate key using ftok");
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return EXIT_FAILURE;
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}
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printf("Generated key using ftok (key = %d)\n", key);
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// ========================================================================
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// Create the first message queue.
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msqid = msgget(key, IPC_CREAT | IPC_EXCL | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
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if (msqid < 0) {
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perror("Failed to create message queue");
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return EXIT_FAILURE;
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}
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printf("Created message queue (id : %d)\n", msqid);
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// ========================================================================
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// Send the message.
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__send_message(msqid, 1, &message, "Hello there!");
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// Receive the message.
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__receive_message(msqid, 1, &message);
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// Create child process.
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if (!fork()) {
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sleep(3);
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// Send the message.
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__send_message(msqid, 1, &message, "General Kenobi...");
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return EXIT_SUCCESS;
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}
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// Receive the message.
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__receive_message(msqid, 1, &message);
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sleep(3);
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// ========================================================================
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// Send the message.
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__send_message(msqid, 7, &message, "course, ");
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__send_message(msqid, 9, &message, "cheers!");
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__send_message(msqid, 1, &message, "From the operating");
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__send_message(msqid, 3, &message, "systems");
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// Receive the message.
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__receive_message(msqid, 1, &message);
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__receive_message(msqid, -8, &message);
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__receive_message(msqid, -8, &message);
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__receive_message(msqid, 0, &message);
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// Delete the message queue.
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ret = msgctl(msqid, IPC_RMID, NULL);
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if (ret < 0) {
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perror("Failed to remove message queue.");
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}
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printf("Correctly removed message queue.\n");
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return EXIT_SUCCESS;
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}
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