© David Gold. Except where the source is noted, this work is licensed under a Creative Commons Attribution License CC-BY 4.0.
Now, as you did in lesson 1, open up your Terminal application
When you click around the folders and subfolders of your computer, you are actually navigating directories. Directories are a hierarchical file system your computer uses to store and organize files.
Let's start by using the pwd (print working directory) command to figure out what directory we're in. Type the following into terminal:
pwd
You should get something like:
/Users/{Your_Computer_Username}
pwd tells you the path of your current directory. The path shows where a file or folder is stored on your computer. The path lists all of the parent directories in the hierarchy, separated by slashes (/), all the way up to the root directory, which is signified by the initial /. When you start up Terminal you should be in your home directory.
To list all files and folders in the current directory, we employ the ls (list) command:
ls
Let's move arond the computer using the cd (change directory) command. If you are in your home directory, you should se the "Desktop" folder when you use the ls command. This is because the "Desktop" is a subfolder in your home directory (in other words, your home directory is the parent directory and your desktop is the child directory).
You can navigate to the Desktop using the cd command:
cd Desktop
Instead of typing out the whole name to a directory or file, try typing part of the name out and hitting the `tab` button. Assuming there are not multiple files and/or folders with the same start, Terminal will auto-fill the word based on the objects in your directory.
In this case, typing "D" + "tab" will probably not work, because you probably have other folders that start with "D" (e.g. Downloads, Documents). But typing "D" + "e" + "tab" probably will work. You should get comfortable using tab to auto-fill names; it makes command line work much easier!
Use the ls command again and you can see all of the files and folders currently on your desktop.
Another way to specify your home directory is by its shortcut, ~. So you can always go direclty to your home directory using the following command:
cd ~
If you know the path to a folder, you can go directly to it using the cd command:
cd ~/Desktop
One last trick; you can use periods as a shortcut to move around directories. One period (.) signifies the folder you are in. Two periods (..) signifies the parent folder. So if you wanted to navigate up two directories you could do the following:
cd ../../
Here is a nice trick if you want to "open" the directory in a more traditional "Finder" window:
open .
The period means that you want to open the current directory. You could open a different folder by providing its path.
Let's start this exercise by making sure we are in the home directory:
cd ~
To make a directory, the command is mkdir (make directory) followed by the name of the directory you want to create. For example, to make a directory called test type the following into Terminal:
mkdir test
You now have an empty directory called test. You can see it if you list the contents of your current working directory.
ls
You can move into this directory with the cd command.
cd test
Verify that you are in the correct directory by checking your path:
pwd
In response the computer should report a path that ends in "test"; for example:
/Users/davidgold/test
Let's now move back into the parent directory:
cd ../
In the same way that one dot (.) represents the current directory (as mentioned in the open . command), two dots (..) means one directory up.
We do not need (nor want) this test directory, so let's delete it. To delete an empty directory, the command is rmdir (__remove directory).
rmdir test
To delete directories with files in them, you need the rm command (discussed later).
For the next exercise, I want to start by making a folder and adding a text file to it:
Make the "test2" directory with mkdir:
mkdir test2
Move into the "test2" directory with cd:
cd test2
Now we're going to use a new command called nano. Nano is a simple text-editor that you can acess from Terminal. You can open the text-editor by simply typing nano into terminal, or you can provide a filename for the text document you want to create:
nano Textfile.txt
This will open the Nano text-editor in Terminal. You can add any text you want, here's an example:
Hello world
Once you've written some text, use the command + x keys to exit Nano. Nano will ask the following:
Save modified buffer (ANSWERING "No" WILL DESTROY CHANGES) ?
Press the y key to save your file. Nano will then double-check what you want to name the file:
File Name to Write: Textfile.txt
If you never provided a file name, you will have the opporutnity to do so now. If you are happy with the file name, hit the enter / return key. This will take you back to the normal Terminal window.
Verfiy that you now have a text file called "Textfile.txt" in your Test folder:
ls
You should get "Textfile.txt" in response.
You can use terminal to look at the contents of a text file without opening it. Copy the command below and paste it into Terminal to create a new file called "File2.txt"
echo -e '1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20' > File2.txt
File2.txt is 20 lines long, containing one number on each line.
To quickly see the first ten lines of this file, you can use the head command:
head File2.txt
It will report the first ten lines, which contain the numbers 1 through 10:
1
2
3
4
5
6
7
8
9
10
To quickly see the last ten lines of this file, you can use the tail command:
tail File2.txt
It will report the last ten lines, which contain the numbers 11 through 20:
11
12
13
14
15
16
17
18
19
20
By defauly, head and tail report ten lines. You can change that number with the -n flag:
head -n 18 File2.txt
The above command will report the first 18 lines of the document.
Let's return to our original text file ("Textfile.txt"). You can rename it using the mv (move) command.
mv Textfile.txt Newfile.txt
Use the ls command again and you should see "Newfile.txt" instead of "Textfile.txt"
You can also move the file (with or without changing the file name) using this command.:
mv Newfile.txt ~/Desktop/Newfile.txt
You have learned some good skills, but now you have some junk spread all over your computer, including a text file on your desktop ("/Desktop/Newfile.txt"), and a folder ("/Test").
You can delete files and folders from your computer using the rm command.
Because of this risk, I recommend that you always inclue the -i flag when running rm; this calls the "interactive mode", meaning terminal will double-check with you before removing objects.
rm -i ~/Desktop/Newfile.txt
If you try deleting the folder in the same way it will not work:
rm -i ~/Test
You will get an error message saying the path is a directory. By default folders with files in them cannot be deleted unless you add the -r (recursive) flag. Recursive mode specifies that you want to delete the folder and all of the files/subfolders within the folder:
rm -ir ~/Test
That is enough for this lesson. There are many other commands that can be used to navigate around your computer using Terminal. I've put together a cheat sheet below for reference:
| command | description |
|---|---|
| cd | Home directory |
| cd [folder] | Change directory |
| cd ~ | Home directory, e.g. 'cd ~/folder/' |
| cd / | Root of drive |
| ls | Short listing |
| ls -l | Long listing |
| ls -a | Listing incl. hidden files |
| ls -lh | Long listing with Human readable file sizes |
| ls -R | Entire content of folder recursively |
| sudo [command] | Run command with the security privileges of the superuser (Super User DO) |
| open [file] | Opens a file |
| open . | Opens the directory |
| top | Displays active processes. Press q to quit |
| nano [file] | Opens the Terminal it's editor |
| pico [file] | Opens the Terminal it's editor |
| q | Exit |
| clear | Clear screen |
| command | description |
|---|---|
| touch [file] | Create new file |
| pwd | Full path to working directory |
| .. | Parent/enclosing directory, e.g. |
| ls -l .. | Long listing of parent directory |
| cd ../../ | Move 2 levels up |
| . | Current folder |
| cat | Concatenate to screen |
| rm [file] | Remove a file, e.g. rm [file] [file] |
| rm -i [file] | Remove with confirmation |
| rm -r [dir] | Remove a directory and contents |
| rm -f [file] | Force removal without confirmation |
| rm -i [file] | Will display prompt before |
| cp [file] [newfile] | Copy file to file |
| cp [file] [dir] | Copy file to directory |
| mv [file] [new filename] | Move/Rename, e.g. mv -v [file] [dir] |
| command | description |
|---|---|
| mkdir [dir] | Create new directory |
| mkdir -p [dir]/[dir] | Create nested directories |
| rmdir [dir] | Remove directory ( only operates on empty directories ) |
| rm -R [dir] | Remove directory and contents |
| command | description |
|---|---|
| more | Output content delivered in screensize chunks |
| > [file] | Push output to file, keep in mind it will get overwritten |
| >> [file] | Append output to existing file |
| < | Tell command to read content from a file |
| command | description |
|---|---|
| [command] -h | Offers help |
| [command] --help | Offers help |
| [command] help | Offers help |
| reset | Resets the terminal display |
| man [command] | Show the help for 'command' |
| whatis [command] | Gives a one-line description of 'command' |