the command line

Objectives

  • Define what the command line is
  • Learn command line navigation and file structure
  • Learn to manipulate files and folders via command line

The command line (or terminal) is a faster and more powerful way to maneuver your operating system than by using a GUI (graphical user interface), such as Windows Explorer or Mac Finder.

Use special keywords to do everything you can with a GUI and more.

What the Command Line Does

Get-Service | Where-Object {$_.Status –eq “Running”}

OSX (Mac) and Linux operating systems are both based on Unix and share many of the same terminal commands.

However, Powershell has adopted aliases that mimic the most common Unix commands.

Note about Windows vs. OSX

Windows has an entirely different kernel (base) and has traditionally had its own command-line syntax for MS-DOS and command prompt.

Powershell ships with all modern Windows systems (since Windows 7) and is a superior shell to command prompt. It compares favorably with Unix-based shells (such as bash).

Powershell

The commands we will learn in Powershell are mostly Unix-like aliases for "cmdlets" that do things like change directories, manipulate files, and so forth.

You can write really powerful scripts with Powershell, which is built on the .NET platform. We will not cover that in this course. 

How we'll use it

We will use the terminal to:

  • navigate around
  • create and remove directories and files
  • move, copy, and paste things
  • use version control (git) to keep track of changes
  • Later, execute Python scripts

INSTALLATION TIME

It's actually not that bad!

Option 1: Mac

Option 2: PC

Option 3: Cloud9

There's a

video for that!

There's a

video for that!

There's a

video for that!

🍏

💻

☁️

(for once)

MAC INSTALLATION

PC INSTALLATION

Cloud9

 INSTALLATION

OS File Structure

Operating Systems organize their folders in a hierarchy (a tree) with parents and children, all relative to a base root directory. 

C:\
Program Files
Users
colt
...

Files and directories have absolute paths based on the root, where each additional level down adds a "\".

C:\Users\colt

The absolute path for "Colt" is:                   

Where am I?

The green directory below is a special directory called "home", which is also known as "~". This is the default directory upon opening your terminal. 

C:\
Program Files
Users
colt ~
...

How do I find out where I am?

The cmdlet "pwd" (print working directory) will tell you the full absolute path of where you're at!

C:\

Program Files

Users
Colt ~
...
stuff
pwd
Path
----
C:\Users\colt\stuff

Navigating Absolutely

The command "cd" ( "change directory") followed by the absolute path of the folder will navigate you directly there.

C:\
Program Files
Users
colt ~
...
stuff
pwd
cd C:\Users
pwd
C:\Users
Path
----
C:\Users\colt\stuff

Navigating Relatively

The dot "." stands for current directory, and dot-dot ".." stands for parent directory. This allows for relative navigation:

C:\
Program Files
Users
colt ~
...
stuff
pwd
cd ..
pwd
Path
----
C:\Users\colt\stuff
C:\Users\colt

What's Inside?

The keyword "ls" will "list" the contents of a directory.

    Directory: C:\Users\colt

Mode                LastWriteTime         Length Name
----                -------------         ------ ----
d-----       12/28/2017   3:31 PM                .config
d-r---         1/5/2018   9:26 PM                Contacts
d-r---        1/10/2018   9:55 PM                Desktop
d-r---         1/5/2018   9:26 PM                Documents
d-r---         1/5/2018   9:26 PM                Downloads
d-r---         1/5/2018   9:26 PM                Favorites
d-r---        1/21/2018   3:03 PM                Google Drive
d-----         2/7/2017   3:49 PM                Intel
d-r---        1/18/2018  11:01 PM                Links
d-r---         1/5/2018   9:26 PM                Music
dar---        1/21/2018   3:03 PM                OneDrive
d-r---         1/5/2018   9:26 PM                Pictures
d-----       12/28/2017   3:21 PM                projects
d-r---         1/5/2018   9:26 PM                Saved Games
d-r---         1/5/2018   9:26 PM                Searches
d-----        1/21/2018   3:31 PM                stuff
d-r---        1/21/2018   3:03 PM                Videos

ls

QUIZ TIME!

Creating Directories

The command "mkdir" ("make directory") followed by the name of the new directory will create a new child directory inside the current directory.

colt ~
mkdir catpics
catpics
stuff
    Directory: C:\Users\colt\stuff

Mode                LastWriteTime         Length Name
----                -------------         ------ ----
d-----        1/21/2018   3:39 PM                catpics
cd catpics

Creating Files

New-Item -ItemType file followed by the filename and file-type extension will create a new file of that type.

colt ~
New-Item -ItemType file favs.txt
catpics
stuff
favs.txt
ls
    Directory: C:\Users\colt\stuff\catpics

Mode                LastWriteTime         Length Name
----                -------------         ------ ----
-a----        1/21/2018   5:28 PM              2 favs.txt

In Powershell, we can create files by putting empty content in them using the New-Item cmdlet.

SUPER QUICK ACTIVITY!

  • Make a new "animals" directory
  • Inside of "animals" create "salamanders" and "frogs" directories
  • Inside of "salamanders" add a new file "axolotl.txt"
  • Inside of "frogs" add a new file:
    PyxicephalusAdspersus.txt (pixieFrog.txt is fine)

axolotls Are awesome

  • Really adorable smile
  • Once worshipped by Aztecs
  • Can regenerate limbs, skin, and spinal cord!
  • 1000x more resistant to cancer than any other animal on earth!
  • They glow in the dark

PIXIE FROGS

Moving / Renaming Things

Files can be moved or renamed using the "mv" (" move") keyword, which takes two arguments: the source and the destination.

Colt ~
mv favs.txt GOAT.txt
catpics
stuff
favs.txt
GOAT.txt
ls
Mode                LastWriteTime         Length Name
----                -------------         ------ ----
-a----        1/21/2018   5:28 PM              2 GOAT.txt
mv GOAT.txt ..
cd ..
ls
Mode                LastWriteTime         Length Name
----                -------------         ------ ----
d-----        1/21/2018   5:33 PM                catpics
-a----        1/21/2018   5:28 PM              2 GOAT.txt

Removing Files

Files can be deleted using the "rm" ("remove") keyword.

Colt ~
catpics
stuff
GOAT.txt

rm GOAT.txt
ls
Mode                LastWriteTime         Length Name
----                -------------         ------ ----
d-----        1/21/2018   5:33 PM                catpics

Removing Directories

Directories can be deleted using the "rm" keyword, with the added option "-r" ("recursive"). You can also add the "-fo" ("force") to prevent warnings. 

Colt ~
ls
catpics
stuff
catpics
rm -r -fo catpics
ls

Warning: "rm -r fo" is a dangerous command! Be extremely careful what folder you pass to it because you will never get it back.

QUIZ TIME!

Recap

  • OS file structure is hierarchical, tree-based
  • Navigate using these commands:
    • cd "change directory"
    • pwd "print working directory"
    • ls "list contents"
  • Remember these aliases:
    • C:\ is root directory
    • ~ is home
    • . is current
    • .. is parent
  • Manipulate files with:
    • "mkdir" create directories
    • "New-Item -ItemType file" create files
    • "mv" move and rename
    • "rm" to remove files, "-r" to remove directories

YOUR TURN

Git

and

github

Posh Git

For Powershell, we can use the Posh Git package here: https://github.com/dahlbyk/posh-git 

YOUR TURN