Lab 2: Forks and Shared Memory

Due: Wednesday, February 1, 2012 by 10:00 PM
Assignment ID: lab2

Lab description

For this lab, complete Programming Problems 3.15 and 3.19. Name the source code file for Programming Problem 3.15 lab2-fork.cpp and for 3.19 lab2-sharedMemory.cpp.

Example Execution

$ ./lab2-fork 23 && ./lab2-sharedMemory 25
Fork example:
0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946, 17711
Shared Memory example:
0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946, 17711, 28657, 46368

Submission

Submit the source code files using the handin program. For example, for this lab, type the following in a terminal exactly as it appears:

  handin  lab2  lab2-fork.cpp  lab2-sharedMemory.cpp

Alternatively, you can submit the assignment from any computer via PeerSpace. After successfully logging into PeerSpace, go to Tools, then Assignments. Click on the Submit link.

Rubric:

Points          Item
----------      --------------------------------------------------------------
                lab2-fork (50 points)
_____ / 15 	Program compiled properly (on ranger2)
_____ / 15 	Proper use of fork
_____ / 15	Proper use of wait
_____ /  5	Executed properly

                lab2-sharedMemory (50 points)
_____ / 10 	Program compiled properly (on ranger2)
_____ / 10	Setting up shared memory (creating, attaching)
_____ / 10	Child process writes to shared memory
_____ / 10	Parent process read from shared memory
_____ /  5	Dettaches shared memory segment
_____ /  5	Executed properly

_____ / 100

Hints

If you get an error like:
```
error: 'shmget' was not declared in this scope
```
or
```
error: 'S_IRUSR' was not declared in this scope
```
use man (e.g., man shmget) or a search engine to determine the appropriate header file to include.
shmget() allocates a specified amount of memory. shmat() returns a pointer to that memory. You set the pointer type based on how you're going to use that memory. Exercise 3.19 dictates what kind of datatype to use.
sprintf() is only for char array. You don't need it for this lab.
If you're having troubles with the shared memory program, temporarily comment out the multi-process code and just write the Fibonacci sequence to shared memory and read it from shared memory (all in a single process). Once you're successful at writing to and reading from the shared memory, add back in the complexity of the child process.