Question

C programming .

Create a tree of processes in the form of an inverted V with two process chains (A and B) as shown in
next figure:

AB A2 B2 An Bn

- To create processes, the program must use the fork () system function and test if
error occurs, not being allowed to use the system () function.

- Each process must wait for its child processes to finish before it finishes itself
(process Xi waits for process X (i + 1) in the chains and process AB waits for processes A1 and
B1).

- The following is an example of program execution, which in addition to being a reference also
shows the messages and output data to be printed by the program:

Inverted V process chain with n = 5:
AB process has PID = 12931

Process A1 has PID = 12932 and PPID = 12931
Process B1 has PID = 12933 and PPID = 12931
Process B2 has PID = 12934 and PPID = 12933
Process A2 has PID = 12935 and PPID = 12932
Process B3 has PID = 12936 and PPID = 12934
Process B4 has PID = 12938 and PPID = 12936
Process A3 has PID = 12937 and PPID = 12935
Process B5 has PID = 12939 and PPID = 12938
Process A4 has PID = 12940 and PPID = 12937
Process A5 has PID = 12941 and PPID = 12940

Example of Tree Diagram in this case :

Answer 1

Here is the C code for the above task:

#include <stdio.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <unistd.h>

int main() {

   int n;

   int i = 1; // loop variable

   printf("Enter value of n: ");

   scanf("%d", &n); // input n

   printf("AB process has pid = %d\n\n", getpid()); // print for AB process

   pid_t pid = fork(); // fork a child process

   if(pid == -1) { // error

       printf("Error!\n");

       return 0;

   }

   else if(pid == 0) { // A1 child process

       printf("Process A%d has PID = %d and PPID = %d\n", i, getpid(), getppid());

       for(i = 2; i <= n; ++i) {

           pid = fork(); // fork child for Ai process

           if(pid > 0) {

               wait(NULL); // make parent process wait for child to finish

               break; // make parent break out of the loop

           }

           printf("Process A%d has PID = %d and PPID = %d\n", i, getpid(), getppid());

       }

   }

   else {

       pid = fork(); // fork another child process

       if(pid == 0) { // B1 child process

           printf("Process B%d has PID = %d and PPID = %d\n", i, getpid(), getppid());

           for(i = 2; i <= n; ++i) {

               pid = fork(); // fork child for Ai process

               if(pid > 0) {

                   wait(NULL); // make parent process wait for child to finish

                   break; // make parent break out of the loop

               }

               printf("Process B%d has PID = %d and PPID = %d\n", i, getpid(), getppid());

           }

       }

       else {

           // make AB process wait for both child to finish

           while (wait(NULL) > 0);

       }

   }

}

Code screenshot:

C main.c )... #include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <sys/wait.h> #include <unistd.h> int main() { int n; int i = 1; // loop variable printf("Enter value of n: "); scanf("%d", &n); // input n printf("AB process has pid = %d\n\n", getpid(); // print for AB process pid_t pid = fork(); // fork a child process if(pid == -1) { // error printf("Error!\n"); return 0; else if(pid == 0) { /A1 child process printf("Process A%d has PID = %d and PPID = %d\n", i, getpido, getppid(); for(i = 2; i <= n; ++i) { pid =_fork(); // fork child for Ai process, if(pid > 0) { wait(NULL); // make parent process wait for child to finish break; // make parent break out of the loop printf("Process A%d has PID = %d and PPID = %d\n", i, getpid(), getppid());

else { pid = fork(); // fork another child process, if(pid == 0) { // B1 child process printf("Process B%d has PID = %d and PPID = %d\n", i, getpido, getppid(); for(i = 2; i <= n; ++i) { pid = fork(); // fork child for Ai process if(pid > 0) { wait(NULL); // make parent process wait for child to finish break; // make parent break out of the loop printf("Process B%d has PID = %d and PPID = %d\n", i, getpido, getppid()); else { // make AB process wait for both child to finish while (wait(NULL) > 0); 46 49 }

Sample IO:

[unseen@x510unr]07:01 pm_$ -/prog/ -> gcc main.c [unseen@x510unr]07:01 pm_$ -/prog/ -> ./a.out Enter value of n: 2 AB process has pid = 22554 Process A1 has PID = 22555 and PPID = 22554 Process B1 has PID = 22556 and PPID = 22554 Process A2 has PID = 22557 and PPID = 22555, Process B2 has PID = 22558 and PPID = 225561 [unseen@x510unr]07:01 pm_$ -/prog/ -> /a.out Enter value of n: 5 AB process has pid = 22560 Process A1 has PID = 22561 and PPID = 22560 Process B1 has PID = 22562 and PPID = 22560, Process A2 has PID = _22563 and PPID = 22561 Process B2 has PID = 22564 and PPID = 22562 Process A3 has PID = _22565 and PPID = 22563 Process B3 has PID = 22566 and PPID = 22564 Process A4 has PID = 22567 and PPID = 22565 Process B4 has PID = 22568 and PPID = 22566 Process A5 has PID = 22569 and PPID = 22567 Process B5 has PID = 22570 and PPID = 22568 [unseen@x510unr]07:01 pm_$ -/prog/C