Foreword

The following exercises needs for you to access a Unix system. A Linux operating system would be better (because I didn't try these exercises on Solaris) but probably not mandatory.

The lecture last week was extremely uncomplete. I will hold some complements on the beginning of the lecture of the 26/04/2005. Look at the new slides for making the exercices.

1. ipcs & ipcrm

• Read the man pages for these two commands.
• If running ipcs show you some already existing IPC, try to identify the program who created it (use ipcs -p).

2. Semaphores

• Read the manual page for man sem.h.
• Try out the examples on the slides.
• Make a critical section that can cope with 2 users maximum and no more. Create 6 clients process which are sleeping for a random amount of seconds and then trying to access the critical section.

3. Message Queue

• Read the manual page for man msg.h
• Try out the examples on the slides.
• Make one process listening to keyboard events with fgets which is sending the key pressed to another process through messages to print it out.

4. Shared Memory

• Read the manual page for man shm.h
• Try out the examples on the slides.
• Do the same than exercise 3, not with a message queue but shared memory (don't forget to protect the access in read/write with semaphores).