Lecture Notes

This is a set of notes that cover CSE 391’s pre-lecture content. It should be used as reference material, but does not replace watching the videos or actively engaging with the content. All the notes are intentionally kept on one page to make searching for content easier. Notes for each lecture will be added on a weekly basis.

These notes were originally written by written by Antonio Ballesteros and Kirupa Gunaseelan, two TAs during the 24wi offering of 391. It has since been refined by TAs and course staff over each offering. Thank you Antonio and Kirupa!

Table of Contents:

1. Week 1: Introduction to Linux

Week 1¶

What is Unix and Linux?¶

Unix and Linux refer to operating systems. You’ve used operating systems before - you might have a PC that runs Windows or a Macbook that runs macOS. We have a “third genre”, which we’ll refer to as Unix/Linux (or sometimes, just Unix or Linux).

It turns out, Unix/Linux computers are by far the most popular operating system today - powering everything from mobile phones and micro-devices to cloud computing and supercomputers.

While learning Linux, we’ll also learn another way for you to interact with your computer.

Accessing Linux¶

Check out the Working at Home page on the class website, which will talk about different ways to access Linux in this class. You’ll need to do this for your homework!

ssh and attu¶

The “default” way we’ll access Linux is by using ssh, which lets you remotely log in to other computers. For example, the attu servers are actually physically located in the basement of the CSE department! Rather than having to physically go to them, we can use ssh to connect to them remotely and do work on them.

The terminal and the shell¶

The terminal is a text-based user interface for interacting with your computer. Inside the terminal is the shell, which is often denoted by the $. Essentially, the shell is a program that allows the user to interact with the operating system + applications.

vim and emacs¶

When editing code on a terminal, we’ll need a code editor. We recommend two in this class - vim and emacs. You only need to pick one of them and stick with them throughout the course. You’ll learn more about these editors in your homework; the editors section of the resources page includes some guides to get started.

Basic Shell Commands¶

Flags and Arguments¶

Flags are prepended with - and change programs’ behavior slightly. For example,

$ ls -l

-l is a flag for ls. In this case, the -l flag for ls lists the content of the current directory in “long listing format”.

Commands can also take arguments. For example,

$ ls dir1

dir is an argument. In this case, this lists the contents of the directory named dir.

Commands can take multiple arguments and flags. For example,

$ ls -a -l dir1 dir2

lists the contents of dir1 and dir2 in long listing format, showing hidden files (-a).

Some programs, like ls, let you combine flags into one -:

$ ls -al dir1 dir2

man pages (documentation)¶

Documentation for Linux is built-in and can be accessed using the man (manual) command.

For example,

$ man ls

provides the documentation for ls.

Some helpful notes for reading man pages:

• most man pages have specific components:
• a summary or synopsis that shows the structure of the command and important flags and arguments
• a longer description that explains each flag and argument
• examples of how to use the command in common use-cases
• you can search for words with /: e.g. typing /reverse searches for "reverse" exactly
• if you type in h, you can see all the commands you can use to navigate a man page

The synopsis has some important syntax. For example, man ls has:

SYNOPSIS
       ls [OPTION]... [FILE]...

• items within [] are optional; in this case, this means that ls can optionally take an OPTION or a FILE, but neither is required.
• the ... mean that the command takes one or more of the preceding item; in this case, this means that ls can take one or more options and one or more files

Compare this synopsis with the next few commands; how are they the same, and how are they different?

Directory Commands¶

Relative Directories¶