Question

6. In POSIX systems (e.g., UNIX, Linux), we use system calls fork() and exec() for process management. Analyze the following programs using the data structures that OS kernels maintain to realize the concept of process. (a) Describe what you would observe and what would happen in the OS kernel if you run this program (the include lines are left out). int main() { fork(); printf("Hello, -CISC3320!\n"); fork(); printf("Hello,CISC3320!\n"); (b) Describe what you would observe and what would happen in the OS kernel if you run this program (the include lines are left out). We assume that you compile this program, the executable is helloapp, and you are running it in the directory where executable helloapp is. int main() { char *args () = {"helloapp", NULL }; char *envs [] = {NULL}; fork(); printf("Hello, -CISC3320 !\n"); execve("./helloapp", args, envs); printf("Hello, -CISC3320!\n");

Answer 1

In section (a) given code will print 6 times the given text. Or we can say there total processes will take place will be six. The tree will go like :(a simple example is given to understand)

id=2 id=3 id=1 Fork Fork U; print (1) fork (); print (2) Forkli printu) fork (1) printai Fare ) prints) fork i printe) V forkl lid=4 folk U print U print (2) pe printing idal values as id= 1 id=2 2 idal 2 id= 3 2 id=4 2 if values are same in printf, they result will be t ttttt ? total 6 outputs.

So, on the OS kernel there the process will make child processes.

Section (b)

Executing given code is an infinite loop, it itself keep executing the file itself.

Our executable file from compiling the program is helloapp. The process is going like:

Executing the executable >> fork() >> exec () with ./helloapp >> it becomes helloapp and ./helloapp to execute it again.

On the OS Kernel, child processes are generated and replaced with a specific function that executes. The function is itself an executable (we're already inside it). So it will be an infinite loop.