Scoroncocolo

On a Windows machine press the Windows key, type "cmd" or "command prompt," and press Enter and BAM!

On a Mac open Applications > Utilities > Terminal, or use Spotlight search (Cmd + Space) and type "terminal" BAM!

On a Mac you can you can r-click any folder in Finder and choose "New Terminal at Folder" and the command line will open with the prompt blinking on that folder (directory)

Moving Around

Think of the Directories on your machine like an upside down tree with the root Directory at the top and all your other directories/folders branching from it

The root directory is denoted by a forward slash in the Terminal (/) and the first directory below the Root Directory is the Users Directory

And next is the Home Directory /Users/username on macOS or C:\Users\username on a PC and that is the location you will find yourself in when you open a fresh Terminal/Command Line session

Lets start in a directory where this webpage was born - a folder inside another folder that is on my Desktop that I've named, appropriately enough, "commandline"

If you were in that directory in the terminal on my Mac and you typed pwd here is the output you would get /Users/stevenhenderson/desktop/websites/commandline which is the Path of the directory in which we are currently in and the command pwd stands for Print Working Directory

And you'll notice that the command prompt is flashing at the end of the word "commandline" which means the Terminal is waiting for another command to be typed so lets type cd .. and hit Enter and now we are one directory up at /Users/stevenhenderson/Desktop/Websites

In the Terminal cd means Change Directory and the command cd .. tells the Terminal to change directories to move up one level in the file directory tree, from your current folder to its "parent" folder, and the command cd ../.. would mean move up two levels

Now that we are at /Users/stevenhenderson/Desktop/Websites type ls and hit Return/Enter and the output will be a list of files because the command ls tells the Terminal to list the files in the current directory

In that list you'll see our old friend "commandline is listed as one of the directories in the list of files so type commandline and hit Enter/Return and you'll be brought right back to /Users/stevenhenderson/desktop/websites/commandline because you can get to any directory you see in that list by typing cd and the name of that folder/directory

Had you typed "desktop" into the command line instead of "commandline" the output would be cd: no such file or directory: desktop Of course that's silly because we know there is a directory named desktop but the Terminal insists we play by its rules and either enter the full path to desktop which is /Users/stevenhenderson/desktop or use the command cd ../.. to move up two levels to /Users/stevenhenderson and from there you can type cd desktop> and Bam! you're there

When you are in a directory and you use the ls command to view the files and folders in that directory you can simply type the name of any directory in that list and hit Enter to go to that directory and a cool thing is you don't have to type the whole word just type the first couple of letters and hit the Tab key and the Terminal will complete the word for you

You should get used to using this handy auto-complete when navigating the command line
For instance if I start at /Users and want to get to my commandline directory I can type cd st and hit the tab key then cd de tab then cd we tab and com tab and suddenly I"m at /Users/stevenhenderson/desktop/websites/commandline

Be aware that although the Terminal is usually not case sensitive if you have named your folders with capital letters you need to use those capital letters to get the Terminal to auto-complete

To quickly move to your Home Directory type cd and the symbol that is called tilde or cd ~

To move quickly to the root directory type cd /

cd .. to go to the parent of your current folder
cd ~ or just cd to jump back to your user’s home directory
cd / to go to the very top of your file system
cd ../.. to move up two levels
cd ../../.. to jump up three levels from your current location

• mkdir Data Makes a new, empty folder/directory named Data
• touch dog.txt Creates a new empty file named dog.txt
• pwd prints the path of the directory you are currently in
• ls lists all files in the current directory/folder
  • ls -a list all files including hidden files
  • ls -l long listing of all files showing owner, size and time last edited
  • ls -R Recursive: Lists everything in the current folder and all subfolders
  • ls .. list the contents of the parent directory one level above
  • mv oldname.txt newname.txt renames files
  • rm filename.txt (remove) permanetly deletes files (caution there be dragons)    there is no cmd + Z or undo
  • rm -r DeadFolder remove/delete a directory/folder and all of its contents (files and sub-directories) permenatly
  • cat AnyFile.txt prints out the entire text of the file
  • head AnyFile.txt prints the first 10 lines of specified file
  • tail AnyFile.txt prints the last 10 lines of specified file
  • echo "Arf! Arf!" > dog.txt replaces any existing text with Arf Arf
  • echo "Arf! Arf! Arf!" >> dog.txt adds text below existing text on dog.txt
  • cp copies files or folders from one location to another
  • say "Everything not forbidden is compulsory" hear your machine speak to you
  • say -f filename.txt Reads the contents of a specific text file aloud
  • history lists a history of your last 16 (in ZSH/macOS) commands
  • history 5 lists your last 5 commands (specify any number you want) and you can use your up arrow to bring them to the command prompt
  • open -a "Sublime Text" dog.txt will open the file in Sublime Text (substitute your code editor) if it is installed on your machine
  • Command + KClears the console's screen
  • Control + Z to pause a process and put it in the background; you can resume it later with the fg command

Here Be Dragons

Far and away the most destructive command you could ever type into the Terminal is rm -rf /* because that tells the Terminal to delete (rm i.e ReMove) the Root Directory and all of its sub-directories from your machine or delete every single file on the entire computer's hard drive starting from the root

The flag -rf tells the computer to carry out the command forcefully and recursively -r (Recursive): Tells the command to look inside directories and delete all their contents (files and sub-directories) -f (Force): Tells the command to ignore read only files and to never prompt for confirmation, even if a file is write-protected

The asterisk overrides the the Linux/Unix kernel failsafe for this command because if you run rm -rf /> without the asterisk the output will be

• rm: rf is dangerous to operate recursively on '/'
• use--no-preserve-root to override this failsafe

and that is where the asterisk comes into play as it will override the failsafe

Unlike the Graphical User Interface (GUI) in Windows, Mac, and even Ubuntu the command line interface (CLI) rarely asks for confirmation when you instruct it to delete, remove or destroy files and/or directories/folders on your machine and there is no "undo" function or command + Z and there is no Trash Folder or Re-Cycle Bin

Once the Terminal deletes something its irretrievably gone

Be extremely careful of typos as rm looks a little like ren or mv as typo can cause unintended consequences

And be extremely careful when you paste anything into the Command Line/Terminal Most often this horribly, dangerous command rm -rf /* is inadvertently pasted at the prompt in the Terminal

We use forward slashes (/) a lot working in the Terminal but a good rule of thumb is to never, EVER run a command where the forward slash is left alone at the end of a command with a space on ether side of it

One of the most frequently used terminal commands is rm -rf ~/.Trash/* and it is a perfectly safe command to run in your console as long as you look hard at it and look hrd at it twice to make sure ther are no typos

The command rm -rf ~/.Trash/* simply deletes all files and folders located inside your personal Trash Directory

Here is a quick breakdown of exactly what each part of the command does:

• rm: Short for "remove," this is the standard terminal command for deleting files
• r (recursive): This tells the command to delete folders and their entire contents, working its way through all nested sub-directories
• f (force): This forces the terminal to delete files without prompting you to confirm each deletion or asking for permission
• ~/.Trash/*: This is the file path directing the command to your personal user account. The ~ represents your home directory, .Trash is the hidden folder where your trashed items live
• And the * acts as a wildcard meaning "everything inside this folder

The rm -rf command forcibly deletes everything it is pointed to without asking for confirmation. If you accidentally add a single space (e.g., typing rm -rf ~/.Trash / instead of ~/.Trash/*), you could accidentally delete your entire hard drive

A good way to play around with this command is inside an OS like Ubuntu on a Virtual Machine

Thanks for the visit