Command line file management

Franklin Bristow

Create, rename, delete, and inspect folder structures on the command-line.
Navigate folder structures on the command-line.

Being connected to a remote computer is nice, but we really want to be able to actually do stuff on that remote computer. The very first thing we’re going to do is to re-do something that we did in the last unit — we’re going to navigate around folder structures and create new folders, ultimately to re-create the folder structure you created in the last unit.

👀 Looking around

When you connect to a remote computer you’re interacting with a program called a “shell”. When you see something that looks like

[you@bird ~]>

the shell is patiently waiting for you to type some commands into it to tell it what to do.

Let’s start by running a command that will ask the shell to print out the contents of the current working directory. Note: the words “directory” and “folder” are synonyms for each other, so any time someone is talking about a directory, they mean folder.

The ls command asks the shell to print out the files and folders that are in the current directory.

Type ls into your terminal, then press Enter:

ls

bin  Mail

The folders that you see here were created for you when your account on the remote computer was created. What you see may not be exactly the same as what is shown here.

🛠️ Making a directory

While bin and Mail are good directories to have, they don’t represent what we want to actually keep on our remote computer, so let’s start making some of our own folders.

We’re going to start small, let’s make a new folder. When we made folders with our visual file explorers we mostly used our mice, though you may have used a keyboard shortcut. While you can literally click on your terminal window, clicking on the terminal window isn’t actually going to do anything other than making a fun clicking sound from your mouse (if you’re literally using a mouse) or a faint tapping sound as you tap your touchpad. Instead, we’re going to need to use a new command to create a folder: mkdir.

The mkdir command will create a new folder that has the name that you pass to it on the command line.

Type mkdir hello into your terminal, press Enter, then re-run ls:

mkdir hello
ls

bin  hello  Mail

You just made a new folder 🎉!

One (minor) problem with making folders in our terminal is that we can’t use spaces ' ' in the same way that we could when making folders in our visual file explorers:

mkdir hello world
ls

hello  world

This didn’t make one folder named hello world, it made two folders, one named hello and one named world. You’ve got a few options:

Don’t use spaces at all and instead use dashes - or underscores _ to represent spaces, or just don’t have spaces (similar to naming variables).
```
mkdir hello-world
mkdir hello_world
mkdir helloworld
```
Put quotes around the name that includes spaces.
```
mkdir "hello world"
mkdir 'hello world'
```
Escape the spaces with a backslash character \.
```
mkdir hello\ world
```

The issue with spaces is common to all commands on the command line. This is a good opportunity to choose a new personal preference: When you’re working on the command line, do you want to always use dashes, underscores, or no spaces at all?

🧭 Navigating directories

Now that we’ve made a directory, we need to be able to “open” the directory. When we used visual file explorers, we “opened” the directory (either in a new window or in the same window) by double-clicking on the icon.

Again, we can double-click on our terminal window, but that double-clicking isn’t doing anything other than making fun clicking or tapping sounds. To “open” a directory that we created, we need to “change” to that directory using a new command: cd

If the name of the folder that you created with mkdir is hello, then you should be able to change into hello with cd:

ls

bin  hello  Mail

cd hello
ls

There should be no output (the directory is empty, you just made it!), but your prompt will change to look something like:

[you@bird hello]>

Now that you’ve changed into a directory, you also need to be able to change out of a directory. When you changed into your directory hello, you moved “down” a folder. You can move “up” a folder by changing to the “parent” directory using a special directory name .. (two periods). You can also go back to your “home” directory (your user folder on this remote computer) by using a special directory name ~ (tilde; I say this as ‘till-duh’, but I’ve also heard ‘till-dee’).

You can change to the parent directory of the current directory (the directory this directory is in) using ...

cd ..

You can change back to your user directory at any time from anywhere using ~.

cd ~

The last part of being able to move around in a directory structure on a remote computer is knowing where you are. Our shell has a concept of a “working directory”. Thinking about visual file explorers, this is the window in our file explorer that we’re currently looking at. We can ask our shell to tell us what directory we’re currently in using the pwd command, pwd stands for print working directory.

Type pwd into your terminal, then press Enter. The directory that you’re currently “in” will be printed out.

pwd

/home/student/you

Now try changing into hello and re-run pwd to see that the directory you’re “in” has changed:

cd hello
pwd

/home/student/you/hello

✏️ Moving and renaming directories

Sometimes when making a directory you realize that you made the directory in the wrong place, or you gave it the wrong name (or misspelled the name).

You can rename or move a directory from one place to another (or both at the same time!) with the mv command.

You can rename a directory with mv.

ls

bin  hello  Mail

We should see a directory named hello because of the mkdir we ran before.

mv hello not-hello
ls

bin  Mail  not-hello

You can move a directory into another directory with mv, too.

# intentionally making two directories
mkdir hello world 
ls

bin Mail hello world

mv hello world/   # move hello *into* world/
cd world          # change into world
ls                # now hello is *in* world/

hello

ls ..         # hello is *not* in ~

bin Mail world

Just like with cd, you can use the special directories .. and ~ to move (mv) a file into the parent directory, list (ls) files in the parent directory, or move (mv) files into your user directory (or list your user directory with ls ~). You can also use another special directory name . (one period) to move something to or from the current directory.

You can move a directory to or from your home directory with ~ and use the . directory to move things into or from the current directory.

cd world
mv hello ~   # move hello to your user directory
ls

There should be no output, we just moved hello out of the directory.

# move hello back into *this* directory
mv ~/hello . 
ls

hello

🗑️ Removing directories

Sometimes you don’t need a directory anymore and you want to remove it. You can remove directories using two different commands: rm and rmdir.

You can remove empty directories using the rmdir command, and this is usually the command you want to use to try removing a directory.

rmdir hello

If you try to remove a directory that has other stuff in it (files or folders), rmdir will warn you and refuse to remove the directory:

mkdir hello
# makes a directory in hello named world
mkdir hello/world 
rmdir hello

rmdir: failed to remove directory 'hello': Directory not empty

You can remove files and directories using the rm command, and you can remove directories that have things in them by asking rm to remove recursively.

rm -r hello # remove hello and all of its contents

The rm command itself will refuse to remove directories unless you tell it to remove them recursively.

rm hello

rm: cannot remove 'hello': Is a directory

The command line doesn’t have a concept of a “temporary trash location” like Windows (the recycle bin) or macOS (the trash can). When you put something into the recycle bin or trash can, you can always open the recycle bin or trash can and get the file back, restoring it to its original location.

When you remove a file or folder on the command line (using rm or rmdir), the file or folder is removed and you can’t get it back, unless you’ve backed it up somewhere.