COSC 350 System Software Lab #9

COSC 350 SYSTEM SOFTWARE
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COSC 350 System Software
Lab #9
How to submit
• For each program, you need write detailed comments for each statement.
• Submit each program by email to cosc350@gmail.com.
• You need demonstrate each task in front of me during the next lab hours.
Task 1: A simple pipe
This task is intended to help your understanding of how pipes work.
A. Copy pipe1.c from BLP, page 532-533.
B. Compile and run it.
C. Reverse the order of the write and read and run the program again.
D. Briefly describe what happened with the reversed order and why the program behaved
that way.
E. Restore the read and write to their original order before proceeding.
F. Modify pipe1.c in the following ways:
a. It's a good idea to define two global integer constants
1. READ_END=0
2. WRITE_END=1
just to help keep straight which is which in the code. For example, when you refer
to the write end of the pipe p, you would then use p[WRITE_END]. Makes the
code much more readable.
b. Dynamically allocate buffer so it's exactly the right size for some_data.
c. Copy the string from some_data into buffer.
d. Modify the read so its third argument is the exact size of buffer (rather than the
large BUFSIZ).
Task 2: Pipes across a fork/exec
A. Copy pipe3.c from BLP, page 535.
B. Copy pipe4.c from BLP, pages 536.
C. Compile and run the program just to see what it does.
D. Modify pipe3.c as follows:
a. Have the parent wait for the child.
b. Close the file descriptor of the write end of the pipe on the parent's side.
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c. Pass the write end of the pipe to the child as a command-line argument.
d. Close the file descriptor of the read end of the pipe on the child's side.
Task 3: Multiple pipes across a fork/exec
In this task, you will write a program that has two-way communication between parent and child.
Use Task 2 as a starting point, and add a second pipe to it.
A. Copy pipe3.c to twoPipesParent.c
B. Copy pipe4.c to twoPipesChild.c
C. Modify twoPipesParent.c as follows:
a. Add a second pipe that will be used for a message from child to parent.
b. Close the appropriate file descriptors on both pipes.
c. Pass both pipes' file descriptors to child in the exec
d. Send the message "Hi there, Kiddo" to child over one pipe (as in Task 2). Print
the pid and byte count as in Task 2.
e. Then, read a message from child over the second pipe. Print the pid, byte count,
and message text as in Task 2.
D. Modify twoPipesChild.c as follows:
a. Grab the file descriptors of both pipes from the argument list.
b. Close the appropriate file descriptors.
c. Read a message from parent over the first pipe (as in Task 2). Print the pid, byte
count, and message text as in Task 2.
d. Then, send the message "Hi, Mom" to parent over the second pipe. Print the pid
and byte count as in Task 2.
E. Print your twoPipesParent.c and twoPipesChild.c to hand in.
F. Run the program multiple times.
Task 4: FIFOs
In this task, you will modify pipe1.c from Task 1 so it uses a fifo instead of a pipe.
A. Copy pipe1.c from Task 1 and name it pipeFifo.c.
B. From your shell, create a fifo /tmp/task4_fifo with appropriate file permissions and
ownership by using mkfifo command.
C. Briefly describe how you created the fifo (the exact command you used). Also describe
another command you could have used.
D. Modify pipeFifo.c so it uses the fifo you created instead of using a pipe.
Task5: Shared Memory
In this task, you need write four programs
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1. buildsm.c build a shared memory which will use for inter process communication
between two process.
2. Removesm.c : remove shared memory buit by buildsm.c
3. Process1.c : process keep send two integer value to shared memory until Cnt-D (end of
data). Before sending data, make sure two integers.
4. Process2.c : get two integer from shared memory and calculate sum of two integer and
display stdout. Process2 will keep running until process1 stop sending data.