The command line (a.k.a terminal, shell, prompt) is another way of interacting with your computer. Instead of working with windows, toolbars, menus, and buttons, you're just interacting with text.
You perform actions by writing commands, and you get your information back from the computer in the form of text. Knowing how to use your command line will be vital to your success as a programmer-- and it's the first place to start getting acclimated to this new way of using your computer.
Both these tutorials can help you get more familiar with the command line
Some people memorize a lot of commands for the terminal, and use terminal-based text applications (e.g., vim or emacs). If you invest enough time in such tools, you can become extremely fast. But it's a big up-front investment, kind of like learning a musical instrument. There are a small set of commands you'll need to get started with the terminal.
You can use the "print working directory" command, pwd, to see which directory you are currently working in. The terminal is always pointing to a particular directory (folder) in your file system. Often, you'll see an indication of this directory in the "prompt": the text immediately above and/or to the left of the line on which you type. The "prompt" (to prompt you to type) varies depending on how your terminal is set up, but it appears every time it's your turn to type. The simplest prompt is just $.
Here's an example of running pwd on the virtual machine you're currently downloading:
Figure 1: pwd
Notice how the prompt (dev@eda: ~) comes right back again? That's why we call it the prompt. (Uh, not because it comes back quickly, but because it keeps prompting you for input.) Also notice that after we typed pwd and hit Enter, the terminal responded by outputting the current working directory (/home/dev) to the next line. That's how the terminal works.
Let's try a few more commands:
We can move up or down directories (folders) by calling "change directory" (cd). There are two special names for folders. The single dot . represents the current directory. The double dot .. represents the parent directory. The "path separator" (between folders) is the /.
So we can move multiple folders at once by stringing them together with /:
Figure 2: cd
Here we went down into the workspace folder (which is a sub-folder in the current folder), then back up two folders to the parent of the current folder, and then back into the current folder. Which leaves us . . . right back where we started! Why would we do this? We wouldn't. It's pointless.
But nevertheless there is a point here, which is that we can combine folder names and .. to move all through the folder hierarchy with a single command. Now let's cd into our workspace folder. This is where you'll do all your work for this course. Keep it all here.
Figure 3: cd workspace
Hey, look! Our prompt has changed. What does all that mean, anyway?
Well, "dev" is our username and "eda" is the name of our computer.
The tilde (~) represents our home folder, in this instance /home/dev. And we're now in the workspace folder inside our home folder, hence ~/workspace. And the $ is the standard prompt. This will change if we start an application, such as a JavaScript REPL (read, evaluate, print loop), but we'll explain that when we come to it.
What if we want to list the files and folders in this folder? We can do that with the list (ls) command. If we want to see more than just the names, we can add "flags" to the command, preceded with a hyphen. The a flag means "all": show all the files, even the hidden ones (files with names starting with a . are hidden usually). The "l" flag means use a long listing format, which gives us extra information. We can combine them thus:
Figure 4: ls and ls -al
Notice that the ls command didn't return anything. That's because our folder is currently empty. But when I use the -a flag, I see the hidden files and folders (beginning with .), too. That includes—and it is no accident that these both start with a dot—the current folder . and the parent folder ...
By using the -l flag as well, I tell the terminal to list more information. So here I see this line for the current folder:
drwxrwxr-x 2 dev dev 4096 Sep 26 22:27 .This tells me a lot, actually, though you don't need to know it all.
dmeans this is a directoryrwxthe first time means that the owner of this folder has read, write, and execute privileges on itrwxthe second time means that the group to which the owner belongs also has read, write, and execute privilegesr-xmeans that all other users can read or execute, but cannot write to this folder2no one really knows what this number means; it probably just got lost and wandered in here for companydevthe first time is the userdevthe second time is the user's "group"4096is the file size in bytesSep 26 22:27is an indication that the author was doing this at the very last minute.is the name of the folder: the current folder
OK, that's enough for the moment. You'll pick these up quickly as you go along. Google around and you'll find plenty of cheat sheets of commands. Print one out and keep it handy, or add a bookmark to it in your browser.
To get out of the shell (terminal), just type exit and hit Enter.
- Cheat sheet (that'll keep ya busy)