Hey guys. I'm very new to Unix. I'm pretty fluent in Java and C, but I have never actually used Unix for anything. I am in an Operating Systems course now and I have an assignment to write a piece of code that involves forks and piping. I'm stuck.

1. The problem statement, all variables and given/known data:

Write a C program that will create three processes as follows:

Code:

         A
        /   \
       /     \
      /       \
   B            C

Connect process B and C with a pipe. Process C will run ls program and send the output into the pipe. Process B will run sort program and sort the list from process C in reverse order. Process A will print "Welcome, friend!" before the list is displayed and print "Good Bye!” after the list is displayed. Do not use the sleep function. Tell me if your program works.


2. Relevant commands, code, scripts, algorithms:

n/a

3. The attempts at a solution (include all code and scripts):

Here's my crack at it...

Code:

#include <stdio.h>
#include <unistd.h>
#include <sys.wait.h>

int main() {
  int pipefd[2];
  int pid1 = 0; int pid2 = 0;
  char *lsArg[2] = {"ls", 0};
  char *rArg[2] = {"-r", 0};
  pipe(pipefd);
 
  pid1 = fork();
  if(pid == 0) {
    dup2(pipefd[1], 1);
    execv("/bin/ls", lsArg);
  }
  else {
    waitpid(pid1, NULL, 0);
  }
}

4. Complete Name of School (University), City (State), Country, Name of Professor, and Course Number (Link to Course):
Rowan University, NJ USA. Professor Xu.
h ttp ://elvis. rowan .edu/~xu/classes/os/os_f12.htm


Now I realize that I do not have the reverse thing in there, nor do I have the Welcome and goodbye message. I'm just trying to figure out where things go and how they really work.

When I run what I currently have, it lists what my "ls" would list in normal order. It also locks up and doesn't ever seem to really finish, and I can't do anything without disconnecting.

Like I said, new to Unix.. any help would be appreciated. Thanks.

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