layout: true <div class=bot-bar> Intro and getting started </div> --- class: center, middle # Introduction and a dash of *nix --- # Overview 1. Command line: what and why? 2. Unix intro 3. Unix command line --- class: center, middle # Getting started --- # What is \*nix? * "\*nix" refers to a group of operating systems either derived from or inspired by the original AT&T Unix from Bell Labs * GNU/Linux is a "Unix-like" * macOS is an actual Unix derivative -- * \*nix systems follow similar principles and provide similar (software) interfaces -- * Unix and its derivatives have entrenched themselves in academia and industry * The many tools developed to run on \*nix systems are mature and are here to stay * General \*nix literacy will help you since you have a pretty good likelihood to be developing on a \*nix system -- * This does not mean that \*nix systems are inherently better than other operating systems like Windows * Windows also has its own set of tools * Some \*nix tools have been ported to Windows * Windows now has WSL(2) that serves as a Linux living inside Windows --- ## What is a command line? * The "command line" is a type of interface where *you provide a line of text* that the interpreting software can interpret into commands to perform * This interpreting software is known as a "shell" * There are also "graphical shells" i.e. the GUIs of Windows and macOS * These take an input like a mouse click on a shortcut and interprets it as a command to launch the appropriate application --- ## Why the command line? * Before we had graphical displays we printers and teletypes (TTYs) * `printf()` literally meant to print -- * We then moved onto video **terminals** * These were a combination display and keyboard, except they could only display text and symbols -- * Nowadays we don't have actual video terminal devices, but we have "virtual terminals" and "terminal emulators" to act like them (e.g. macOS Terminal, iTerm 2, Command Prompt) -- * Unix and the many tools for it were developed during these times * Text serves as a long lasting, reliable interface that is very easy to automate * Count the number of GUI changes to Windows, macOS, Android, and iOS over the years * How would you automate a GUI? -- * It probably would be more work than writing some commands to be run --- ## Command line basics * We will focus on the \*nix command line shell in this class * (From now on, when I say "shell" by itself I mean command line shell) -- * Shells follows very similar basic syntax no matter what shell (bash, zsh, csh, etc.) you use -- * Shells provide you an interface to interact with the system via its directories (folders) and files * You can navigate through directories * You can modify files * You can launch applications * Most shells feature some sort of *tab completion*, where hitting the Tab key will make the shell try to finish a partially typed word --- ## Command structure ```bash $ <command> <argument 1> <argument 2> <argument 3> ^ ^ ^ ^ | | | |-- programs are provided these to | | | interpret (remember argc and argv[]?) | | | | | |-- words separated by whitespace | | | |-- certain things are actual programs, certain things | are handled by the shell ("built-ins") | |-- this is called a "prompt" and can take many forms ``` --- ## \*nix and the filesystem * As a spoiler for a future lecture, \*nix exposes everything as a file * Navigating through directories (folders) and interacting with files is a fundamental task * We address and locate files via "paths" * Each running program (including the shell) has a "current working directory" * `/` enters/separates directories * `.` refers to the current directory * `..` refers to the "parent" directory (the directory that contains the current directory) --- ## \*nix and the filesystem ### Types of paths: * Absolute: starts with `/` * We call `/` the "root directory"; the starting point of the filesystem * `/home/brandon/Music/deemo-saika-rabpit.flac` * Relative: starts from current or parent directory * `./dir1/dir2` * `../../some-dir` * Implicitly starts from the current directory if the path doesn't start with `/`, `.`, or `..`: `dir1/dir2` --- ## Important commands * `man`: "manual pages": gives info on programs * `pwd`: "print working directory": tells you your current directory * `ls`: "list": lists the contents of a directory * `cd`: "change directory": changes your current directory * `mv`: "move": moves files to another directory (actual moving) or another filename (renaming) * `cp`: "copy": copies files * `touch`: creates an empty file if one doesn't exist (otherwise updates its timestamp) * `rm`: "remove": deletes files * `grep`: searches files for data matches * `cat`: "concatenate": technically concatenates files, often used to print out a file's contents * [Wikipedia has a nice list commands that \*nix systems typically come with](https://en.wikipedia.org/wiki/List_of_Unix_commands) --- ## Some common conventions * Lots of commands/programs act on files * A common pattern is `command path-to-file` e.g. text editors * `nano some-file.txt` * `vim some-code.cpp` * `--help` as an argument is a common way to get info on how to use command * `cat --help` --- ## Playing with output * You can pipe output from command to another command with a pipe (`|`) * `echo "hello world" | rev` * You can save output from a command to a file with a "redirection" (`>`) * `echo "hello world" > some-file` * You can retrieve input from a file for a command with another "redirection" (`<`) * `rev < some-other-file` * More to come in a future lecture ... --- ## Intro to automation * You can save a list of commands into a file * This is known as a "script" * You can now run this script whenever you want by invoking the filename as an argument for your shell of choice * `$ bash myscriptfile` * This runs a new shell instance that runs each of those commands as if you had entered in the commands yourself * If the file is marked as executable, you can also directly invoke it as a program * `$ ./myscriptfile` * Note you have to specify it as an explicit path (i.e. has a `/` present) * We'll discuss the specifics of this in a future lecture --- <!-- page.content is pre-rendering -->