The notes below are modified from the excellent Unix Shell tutorial that is freely available on the Software Carpentry website. I highly recommend checking out the full version for further reading. The material is being used here under the terms of the Creative Commons Attribution license.
We now know how to explore files and directories,
but how do we create them in the first place?
Let's go back to our
data-shell directory on the Desktop
ls -F to see what it contains:
$ ls -F
creatures/ molecules/ pizza.cfg data/ north-pacific-gyre/ solar.pdf Desktop/ notes.txt writing/
Let's create a new directory called
thesis using the command
(which has no output):
$ mkdir thesis
As you might guess from its name,
mkdir means "make directory".
thesis is a relative path
(i.e., doesn't have a leading slash),
the new directory is created in the current working directory:
$ ls -F
creatures/ north-pacific-gyre/ thesis/ data/ notes.txt writing/ Desktop/ pizza.cfg molecules/ solar.pdf
Good names for files and directories
Complicated names of files and directories can make your life painful when working on the command line. Here we provide a few useful tips for the names of your files.
Don't use whitespaces.
Whitespaces can make a name more meaningful but since whitespace is used to break arguments on the command line is better to avoid them on name of files and directories. You can use
_instead of whitespace.
Don't begin the name with
Commands treat names starting with
Stick with letters, numbers,
Many other characters have special meanings on the command line. We will learn about some of these during this lesson. There are special characters that can cause your command to not work as expected and can even result in data loss.
If you need to refer to names of files or directories that have whitespace
or another non-alphanumeric character, you should surround the name in quotes (
Since we've just created the
thesis directory, there's nothing in it yet:
$ ls -F thesis
Let's change our working directory to
then run a text editor called Nano to create a file called
$ cd thesis $ nano draft.txt
Let's type in a few lines of text.
Once we're happy with our text, we can press
Ctrl-O (press the Ctrl or Control key and, while
holding it down, press the O key) to write our data to disk
(we'll be asked what file we want to save this to:
press Return to accept the suggested default of
Once our file is saved, we can use
Ctrl-X to quit the editor and
return to the shell.
nano doesn't leave any output on the screen after it exits,
ls now shows that we have created a file called
When we say, "
nano is a text editor," we really do mean "text": it can
only work with plain character data, not tables, images, or any other
human-friendly media. We use it in examples because it is one of the
least complex text editors. However, because of this trait, it may
not be powerful enough or flexible enough for the work you need to do
after this workshop. On Unix systems (such as Linux and Mac OS X),
many programmers use Emacs or
Vim (both of which require more time to learn),
or a graphical editor such as
Gedit. On Windows, you may wish to
use Notepad++. Windows also has a built-in
notepad that can be run from the command line in the same
nano for the purposes of this lesson.
No matter what editor you use, you will need to know where it searches for and saves files. If you start it from the shell, it will (probably) use your current working directory as its default location. If you use your computer's start menu, it may want to save files in your desktop or documents directory instead. You can change this by navigating to another directory the first time you "Save As..."
Let's tidy up by running
$ rm draft.txt
This command removes files (
rm is short for "remove").
If we run
its output is empty once more,
which tells us that our file is gone:
Deleting Is Forever
The Unix shell doesn't have a trash bin that we can recover deleted files from (though most graphical interfaces to Unix do). Instead, when we delete files, they are unhooked from the file system so that their storage space on disk can be recycled. Tools for finding and recovering deleted files do exist, but there's no guarantee they'll work in any particular situation, since the computer may recycle the file's disk space right away.
Let's re-create that file
and then move up one directory to
$ nano draft.txt $ ls
$ cd ..
If we try to remove the entire
thesis directory using
we get an error message:
$ rm thesis
rm: cannot remove `thesis': Is a directory
This happens because
rm by default only works on files, not directories.
To really get rid of
thesis we must also delete the file
We can do this with the recursive option for
$ rm -r thesis
With Great Power Comes Great Responsibility
Removing the files in a directory recursively can be very dangerous
operation. If we're concerned about what we might be deleting we can
add the "interactive" flag
rm which will ask us for confirmation
before each step
$ rm -r -i thesis rm: descend into directory ‘thesis’? y rm: remove regular file ‘thesis/draft.txt’? y rm: remove directory ‘thesis’? y
This removes everything in the directory, then the directory itself, asking at each step for you to confirm the deletion.
Let's create that directory and file one more time.
(Note that this time we're running
nano with the path
rather than going into the
thesis directory and running
$ mkdir thesis $ nano thesis/draft.txt $ ls thesis
draft.txt isn't a particularly informative name,
so let's change the file's name using
which is short for "move":
$ mv thesis/draft.txt thesis/quotes.txt
The first parameter tells
mv what we're "moving",
while the second is where it's to go.
In this case,
which has the same effect as renaming the file.
ls shows us that
thesis now contains one file called
$ ls thesis
One has to be careful when specifying the target file name, since
silently overwrite any existing file with the same name, which could
lead to data loss. An additional flag,
mv -i (or
can be used to make
mv ask you for confirmation before overwriting.
Just for the sake of consistency,
mv also works on directories
quotes.txt into the current working directory.
mv once again,
but this time we'll just use the name of a directory as the second parameter
mv that we want to keep the filename,
but put the file somewhere new.
(This is why the command is called "move".)
In this case,
the directory name we use is the special directory name
. that we mentioned earlier.
$ mv thesis/quotes.txt .
The effect is to move the file from the directory it was in to the current working directory.
ls now shows us that
thesis is empty:
$ ls thesis
ls with a filename or directory name as a parameter only lists that file or directory.
We can use this to see that
quotes.txt is still in our current directory:
$ ls quotes.txt
cp command works very much like
except it copies a file instead of moving it.
We can check that it did the right thing using
with two paths as parameters --- like most Unix commands,
ls can be given multiple paths at once:
$ cp quotes.txt thesis/quotations.txt $ ls quotes.txt thesis/quotations.txt
To prove that we made a copy,
let's delete the
quotes.txt file in the current directory
and then run that same
$ rm quotes.txt $ ls quotes.txt thesis/quotations.txt
ls: cannot access quotes.txt: No such file or directory thesis/quotations.txt
This time it tells us that it can't find
quotes.txt in the current directory,
but it does find the copy in
thesis that we didn't delete.
cp old newcopies a file.
mkdir pathcreates a new directory.
mv old newmoves (renames) a file or directory.
rm pathremoves (deletes) a file.
- Use of the Control key may be described in many ways, including
- The shell does not have a trash bin: once something is deleted, it's really gone.
- Depending on the type of work you do, you may need a more powerful text editor than Nano.