-ORIENTED

COMMAND LINE
Tutorial
nter pwd again and you’re back in the home folder.
ow try it using an absolute path. nter
cd /
and youll be in the root directory. nter ls to view
the folders at the base of your hard drive. nter
cd /home/pi
…to move back to your home folder. There’s a
shortcut for this:
cd ~
The tilde (~) character is a shortcut for your home
folder. You can use it at the start of an absolute
directory too. For instance, entering:
> Owner: Typically this will be the person who created
the account.
> Group: This is a group of users. You have only one
group, pi, by default, containing just one
user (also pi).
> Other: These are users from other systems.
ach of the three groups contains letters rw. hese
letters are always in that order and each is either the
letter or a hyphen. A letter indicates that the person,
group, or other has access to read, write, or execute the
file. hyphen means they dont have that level of access.
Some examples include:
> rwx read, write, and execute
> rw- read, write, but don’t execute
> r-x read and execute
> r-- read only
cd ~/Downloads
…moves to your Downloads folder no matter where
you are in the system.
Files
hroughout the file system, youll find various types
of files. good selection is in the python_games
folder, so enter:
cd ~/python_games
ls -l
Now that you’ve discovered how to move around the
file system from the command line, its time to learn
what else you can do.
Take command
ne of the first commands you need to learn is mkdir.
This stands for ‘make directory’. Move to the home
folder and create a new directory called test:
cd ~
mkdir test
cd test
The -l part (an option) makes it use ‘long listing’
mode, which displays items with lots of information:
-rw-rw-r-- 1 pi pi 973 Jan 27 2015
4row_arrow.png
From left to right, each item is:
> Permissions: The users and groups that
can access a file.
> Hard links: he number of files that
are lined to this file.
> Owner: he person who owns the file.
Usually either pi or root.
> Group: he group the file belongs to.
> File size: he name of the file.
> Modification hen the file was last changed.
> File name: he name of the file.
The most obscure item is the list of letters
and hyphens that make up the permissions.
he first letter will be either a or a d
depending on whether its a file or a directory. ur
4row_arrow.png is a file, so its a .
After that are nine letters arranged into three
groups of three (see Fig 1 overleaf):
TAB COMPLETION
The single most useful tip you’ll ever learn for the
command line is tab completion. Pressing TAB at any
time when entering a working path attempts to complete
the le or irector name for o e cd python_games
and enter xdg-open Tr, then press the TAB key. Notice
ho it ll it ot to ‘xdg-open Tree_’. There are three
le tarting ith ree ickl re TAB twice and you’ll
see them: Tree_Short.png, Tree_Tall.png and Tree_Ugly.
png. Enter S, T, or U and press TAB again to ll ot the
hole le name Pre RETURN to open it.
a comletion can e inalale for entering long le
names packed with letters, numbers, and punctuation.
raspberrypi.org/magpi
February xxxxx 2016 2017
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