Interacting with the filesystem

Ok, so you have a terminal and you can run some commands... what now?

The next few pages show a quick demo of some of the kinds of things you can do. We'll start by learning to move around through the directory structure, and create simple directories and files.

Directories (also known as folders)

If you typed pwd in the earlier examples you'll have seen something like this:

% pwd
/home/duncan

The directory output by pwd is your current working directory - it tells you where you are in the filesystem. Your terminal is always 'in' some directory on your filesystem, and right now it is in this one.

Note

A 'directory' is just a folder that contains files - just as you would see in Explorer on Windows or Finder on a Mac. We will generally use the words 'folder' and 'directory' interchangeably.

Unless you have done something to change it, the current directory will be your home directory. It will look like /home/<your username> or maybe /Users/<your username>. This directory is so useful it also has a special name: "~". So you can always get back there by typing

% cd ~

(cd stands for 'change directory'.)

Happily, everything in your home directory belongs to you, so you can safely change things without worrying that you might affect something important that other people are using.

(Depending on your system, the current working directory is probably also displayed in your prompt.)

Making and moving between directories

Let's make a directory to do some work in - using the mkdir command:

% mkdir bash_tutorial

(mkdir stands for "make directory") and then let's change directory into it:

% cd bash_tutorial

Run pwd again; you should now see something like /home/duncan/bash_tutorial - you are now 'in' the new subfolder you created.

To get back to your home folder again, you can type one of these commands:

% cd ..

OR

% cd ~

The first of these (cd ..) always moves up one level to the parent directory of where you are currently. While, as described above, the second command always changes back to your home folder from wherever you are.

Note

There's one other place you might like to go - the root of the whole filesystem hierarchy. It is called /.

% cd /

If you type ls now you'll see all the top-level directories in the whole filesystem.

To go further though, let's get back to our bash_tutorial directory inside our home directory:

% cd ~/bash_tutorial

This command uses a whole directory path - ~/bash_tutorial. The first part (~) is your home directory, and the second part (bash_tutorial) is the subdirectory of your home directory we just created. The are separated in the path by the directory separator /.

Moving faster

You may already be getting tired of typing these long directory names. Luckily BASH has a very important feature known as 'tab completion' that does it for us. This is best learnt by trying it - let's try that last one again. First let's cd to your home directory:

% cd ~

To change back into our bash tutorial this time, try typing just cd ba and then press <tab>.

What you should see is that BASH has figured out that you must have meant bash_tutorial (because there aren't any other files or folders starting with 'ba' in there) so it has auto-completed it for you.

This makes finding your way through folders much quicker. Try it on some other folders, like ~/bash_tutorial/archive for example.

Question

What happens if there are two files starting 'ba' in the folder? (Try it by making another one.) Hint. Try pressing <tab> a few times.

Making some files

Right now there's nothing in this directory (since we just created it). Let's create some files so we have a more realistic-looking directory:

% touch bash_intro1.md  bash_intro_2012.md  bash_intro2.md
% touch bash_introduction.doc  bash_intro.md  bash_intro.md.old
% touch .very_secret

The touch command just creates new, empty files (if they don't exist already) - check using ls:

ls

You should see something like:

bash_intro1.md      bash_intro2.md         bash_intro.md
bash_intro_2012.md  bash_introduction.doc  bash_intro.md.old

Note

What happened to .very_secret? Because it starts with a ., it is a hidden by default. To see it you have to use ls -a:

% ls -a
.             bash_intro.md      bash_intro2.md
..            bash_intro.md.old  bash_intro_2012.md
.very_secret  bash_intro1.md     bash_introduction.doc

Now we can see .very_secret, along with the dummy entries . (which means "this directory") and .. (which means "the parent directory").

Hmm, these files are a bit messy! Let's make another new folder and tidy away some of those files.

% mkdir archive

Type ls to list the directory again and check that archive has been created:

archive         bash_intro_2012.md  bash_introduction.doc  bash_intro.md.old
bash_intro1.md  bash_intro2.md      bash_intro.md

We'll use the mv command to move some of those files into the archive folder:

mv bash_intro.md.old bash_introduction.doc archive/

mv stands for "move", and allows you to move files from one place to another. In the form above it takes the files represented by all positional arguments except the last one and puts them in the directory which is its final argument.

mv can also be used to rename files:

% mv bash_intro_2012.md bash_intro_oldest.md

It even works on directories

% mv archive old

Another thing you could do is copy files instead of moving them - this uses the command cp instead:

% cp bash_intro.md bash_intro_final.md

Question

Check what's in the folder now with ls. Does it match what you expect?

Removing files and folders

Our 'bash_tutorial` folder is still a bit messy:

% ls
bash_intro.md   bash_intro2.md       bash_intro_oldest.md
bash_intro1.md  bash_intro_final.md  old

Let's clean it up a bit more by deleting some files. To remove files you can use the rm command:

% rm bash_intro2.md

If you want to remove a directory, you can use rmdir, however there's a caveat:

rmdir old

This will probably say:

rmdir: failed to remove 'old': Directory not empty

This is because rmdir only works if the directory is empty. (This is a good thing as it can stop you accidentally deleting lots of files.)

If you really want to remove a whole folder and all its contents, you can pass the -r argument to rm, which tells it to remove the directory "recursively":

rm -r old

Type ls to check the directory has been removed.

Finally, if you want to operate on multiple files at the same time - for example to delete all files those starting with a particular name - you can use the wildcard character *. To demonstrate, let's create some files now:

touch for_deletion_1.txt for_deletion_2.txt for_deletion_3.txt

...and remove them again:

rm for_deletion*.txt

Caution

These commands delete files permanently - you can't get them back. And they don't ask for confirmation!

You shouldn't run them until you are 100% certain what files they will affect.

Especially when using wildcards, you should always try to use ls first to verify what will be deleted, e.g.:

ls for_deletion*.txt

## Next steps

Go and read some important facts about filenames.