COMP9812 Operating Systems: Interprocess Communication & Solution

This assignment solution focuses on interprocess communication (IPC) and synchronisation within an operating system context. It tackles the producer-consumer problem through several tasks. These tasks include creating and destroying shared memory segments, sending single and multiple messages between producer and consumer processes, implementing variable producer delays, utilizing semaphores for synchronisation, and constructing a character-based circular buffer. The code examples are provided in C programming language and are designed for a Unix/Linux environment, demonstrating practical applications of IPC concepts like shared memory and mutual exclusion. This solution would be helpful for students studying operating systems concepts and seeking practical implementation examples.

Operating System

Table of Contents
Task 1: Create and destroy a shared memory segment........................................................1
Task 2: Send a single message from producer to consumer.................................................1
Task 3: Send a series of messages between producer and consumer..................................1
Task 4: Variable producer delay............................................................................................1
Task 5: Implement semaphores..............................................................................................1
Task 6: Character-based circular buffer...............................................................................1
1

Task 1: Create and destroy a shared memory segment
Producer.c
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#include<time.h>
#define SHSIZE 100
int main(int argc,char*argv[])
{
int shmid;
key_t key;
char * shm;
char*s;
key=9876;
shmid=shmget(key,SHSIZE,IPC_CREAT | 0666);
if(shmid<0)
{
perror("shmget");
exit(1);
}
shm=shmat(shmid,NULL,0);
if(shm==(char*)-1)
{
perror("shmat");
exit(1);
}
memcpy(shm,"hello world",11);
s = shm;
s += 11;
2

*s = 0;
{
int nanosleep(const struct timespec *req,struct timespec *rem);
{
while(*shm != '*')
nanosleep (1);
return 0;
}
}
}
Output
3

4

Task 2: Send a single message from producer to consumer
Consumer.c
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#define SHSIZE 100
int main(int argc,char*argv[])
{
int shmid;
key_t key;
char * shm;
char*s;
key=9876;
shmid=shmget(key,SHSIZE,IPC_CREAT | 0666);
5

if(shmid<0)
{
perror("shmget");
exit(1);
}
shm=shmat(shmid,NULL,0);
if(shm==(char*)-1)
{
perror("shmat");
exit(1);
}
for(s =shm; *s !=0; s++)
printf("%c", *s);
printf("\n");
*shm = '*';
return 0;
}
6

Output
7

Task 3: Send a series of messages between producer and consumer
Producer.c (send message)
Producer.c
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#include<time.h>
#define SHSIZE 100
int main(int argc,char*argv[])
{
int shmid;
key_t key;
char * shm;
8

char*s;
key=9876;
shmid=shmget(key,SHSIZE,IPC_CREAT | 0666);
if(shmid<0)
{
perror("shmget");
exit(1);
}
shm=shmat(shmid,NULL,0);
if(shm==(char*)-1)
{
perror("shmat");
exit(1);
}
memcpy(shm,"hello world",11);
s = shm;
s += 11;
*s = 0;
{
int nanosleep(const struct timespec *req,struct timespec *rem);
{
while(*shm != '*')
nanosleep (1);
return 0;
}
}
}
9

Output
Consumer.c (receive message)
Consumer.c
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#define SHSIZE 100
int main(int argc,char*argv[])
10

{
int shmid;
key_t key;
char * shm;
char*s;
key=9876;
shmid=shmget(key,SHSIZE,IPC_CREAT | 0666);
if(shmid<0)
{
perror("shmget");
exit(1);
}
shm=shmat(shmid,NULL,0);
if(shm==(char*)-1)
{
perror("shmat");
exit(1);
}
for(s =shm; *s !=0; s++)
printf("%c", *s);
printf("\n");
*shm = '*';
return 0;
}
11