Here is a general outline of the key concepts and commands (arranged by topic) that you should know for Exam 01.

Introduction

Concepts

• What is Unix?

• What is a shell?

• How would do you use git to:

  • Create a copy a repository.

  • View the changes you've made.

  • Save a change you've made.

  • Share the changes you'ved made.

  • Retrieve the changes from a remote location.

• What are environment variables? What does the PATH environment variable control? How would you modify it?

Commands

1. git

   Version control system for managing our files.

Files

Concepts

• What is a file?

• What is the general layout or hierarchy of a typical Unix filesystem?

• What is an inode and what information does it store?

• What is the difference between an absolute and relative path?

• How do Unix file permissions work? How would you set them to restrict access for certain operations and certain classes?

  You should be able to translate from octal to rwx triplets and back.

• What is the difference between a hard link and a soft link?

Commands

1. ls

   List the contents of a directory (long, human-readable, sorted)

2. chmod

   Set permissions using octal and symbolic arguments.

3. stat

   View the inode information fora file.

4. du

   View the total disk usage for a file or directory.

5. ln

   Create hard and soft links.

6. find

   Search directory for files by name and type.

Process

Concepts

• What is a process? What attributes does it have?

• What does it mean to signal a process? What do different the different signals do (TERM, INT, KILL, HUP)?

• How do we suspend, foreground, and background a process?

Commands

1. ps

   List the processes for the current user and for the whole system.

2. top

   Interactively view and manage processes.

3. kill

   Signal a process by PID.

4. time

   Measure how long it takes a process to execute.

5. pkill

   Signal a process by name.

I/O Redirection

Concepts

• What three files does every process start with?

• How do you redirect the output of a command into a new file?

• How do you redirect the output of a command and append it to a file?

• How do you redirect the output of one command as the input to another?

• How do you direct the contents of a file into the input of command?

• What is /dev/null? How would you use it to output stderr but ignore stdout of a program?

• What is a here document and how would you use it?

Commands

1. tee

   Redirect stdin to both stdout and a file.

2. write

   Write to another users terminal.

Networking

Concepts

• What is bandwidth and latency? How are they different? How would we measure both of them?

• What is an IP address? How is a domain name related to it?

• What is a network port?

• What is the basic difference between TCP and UDP?

• How does HTTP work? How would you manually perform a HTTP request?

Commands

1. scp / sftp / rsync

   Transfer a file from one machine to another.

2. ip / ifconfig

   List the IP addresses of the current machine.

3. tmux / screen

   Maintain a persistent shell session.

4. nc / telnet

   General purpose tools to communicate with TCP-based network services.

5. wget / curl

   Communicate using HTTP (ie. download files from the web).

Developer Tools

Concepts

• What exactly happens when you compile a program (ie. describe the compiler pipeline)? What are do the compiler flags -std=c99, -Wall, -g, and -O2 do?

• What is the difference between a dynamic executable and a static executable?

• What is a shared library? How does the environment variable LD_LIBRARY_PATH affect shared libraries? How do we list the shared libraries an executable requires?

• How does make work?

  You should be able to write Makefiles that utilize rules, pattern rules, variables, and magic variables.

• What are some different ways to debug an application? How would you track down a memory error?

Commands

1. gcc

2. ldd

3. make

4. valgrind

5. gdb