Checklist 04

This is a general outline of the key concepts (arranged by topic) that you should know for the Exam 04.

Format¶

The exam will have the following format:

A. Scripting

1. Shell (multiple choice, fill-in-the-blank).

2. Python (multiple choice, fill-in-the-blank).

B. C

1. Pointers, Arrays, Strings/Memory Allocation (multiple choice, fill-in-the-blank).

2. Memory Management/Linked Lists (multiple choice, fill-in-the-blank).

C. System Calls

1. Files (multiple choice, fill-in-the-blank).

2. Processes (multiple choice, fill-in-the-blank).

3. Networking (multiple choice, fill-in-the-blank).

D. Programming

1. Write a Shell script that navigates unix file system.

2. Write a Python script that processes data.

3. Write a C program that uses system calls.

Parts A, B, and C are to be done first on paper. Once that portion is completed and submitted, you will do part D on your own computer and submit code to your assignments repository.

Logistics¶

Exam 04 will take place on Monday, May 5 from 4:15 PM - 6:15 PM in 101 DeBartolo Hall.

As noted above, the first portion of the exam with be on paper, while the remaining component with require coding and submitting work to your assignments repository on GitHub.

During the paper portion of the exam, students will only be allowed to use four cheatsheets. This paper component of the exam must be submitted before students can access the coding section.

For the coding portion, students will use their own computer, and thus are permitted access to any material in their textbooks, notes, assignments, and the Internet.

Scripting¶

1. What is Unix?

   • What are the three tenets of the Unix Philosophy?

   • What are filters? What do they do and how are they related to the Unix Philosophy?

   • What happens during I/O redirection?

2. What is concurrency and what is parallelism?

   • What makes concurrency challenging?

   • What are some different types of parallelism?

   • What are some common examples of these types of parallelism?

Shell¶

How do you construct a unix pipeline to do the following:

1. Extract a fields or characters.

2. Search based on a pattern.

3. Count the number of lines.

4. Search a directory based on a pattern or file attribute.

5. List the processes on the current machine.

Python¶

1. How do you use map, filter, and lambda?

2. How do you use list comprehensions?

3. How do you use generator expressions?

4. How do you sort data?

5. How do you split and join strings?

C¶

1. Why bother with C? Why not just Python or C++?

2. Why is C considered a systems programming language?

3. What is C's relationship to Unix?

Pointers, Arrays, Strings¶

1. What exactly is a pointer? array? string? How are they related?

2. What does it mean to dereference a pointer?

3. How do we get the address of a variable?

4. What are multiple ways to access an element of an array or string?

Memory Allocation¶

1. What is the difference between a struct and a union?

2. How much memory is allocated when we declare an int, float, double, char, int8_t, int32_t, int64_t, size_t, array, string, or pointer?

3. When we declare a variable, where is the data allocated (stack, heap, data, code)?

Memory Management and Linked Lists¶

1. How do we dynamically allocate memory? How do we deallocate that memory?

2. When should we allocate on the stack? heap? data? What are the advantages and disadvantages of utilizing each memory segment?

3. What is singly linked list? doubly linked list?

   • How would we insert an entry into a linked list?

   • How would we search for an entry in a linked list?

   • How would we remove an entry in a linked list?

System Calls¶

1. What exactly are system calls? How are they different from normal functions?

2. What are some reasons why system calls related to files, processes, and networking would fail?

   • How could these system calls fail?

   • How do we check these failures?

   • How do we get the error message related to these failures?

Files¶

1. What is the difference between open and fopen?

2. What exactly is a file descriptor and what system calls can we do with one?

3. How do we get the inode information for a file?

Processes¶

1. What is a process?

   • What attributes or components does it have?

   • What system calls can you do with them?

2. What happens during the life cycle of a typical process?

   • After a fork, how does a process determine if they are the child or parent?

   • After a fork, who executes first: parent or child?

   • What happens when a process performs exec?

   • Why is it necessary to perform a wait?

   • What is the purpose of exit?

3. How do we prevent a fork bomb?

   • How do we prevent zombies?

   • Why would we want to prevent these situations?

4. What is a signal?

   • What does a signal do to a process?

   • How do we send a signal to another process?

   • How do we catch a signal and handle them?

/* forking.c */

#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

int main(int argc, char *argv[]) {
    int status = 0;

    for (int i = 1; i < argc; i++) {
        pid_t pid = fork();

        if (pid < 0) {
            return EXIT_FAILURE;
        }

        if (pid == 0) {
            execlp(argv[i], "forkit", NULL);
        }
    }

    for (int i = 1; i < argc; i++) {
        int child_status;
        while (wait(&child_status) < 0) {
            status += child_status;
        }
    }

    return status;
}

Networking¶

1. What is networking?

   • What is bandwidth and latency and how do we measure them?

   • What is an IP address and what is a domain name?

   • What is a network port?

   • What is the basic difference between TCP and UDP?

2. What is a URL and what are its components?

3. How are sockets like files? How are they different?

4. What is HTTP?

   • What system calls does a typical HTTP client perform? What messages does it send and receive?

   • What system calls does a typical HTTP server perform? What messages does it send and receive?