Shell Scripting Tutorial-2: Shell; Kernel; Terminal & More Video Lecture | Shell Scripting: Discovering to Automate Command-Line Tasks - Back-End Programming

hello guys my name is mother and welcome
to my channel this is the second
tutorial in this series of tutorials on
UNIX shell programming when we learn a
new language what we do is we first
learn the alphabets then we learn to use
the alphabets to form words and then we
learn to use those words into sentences
now we are going to follow a similar
approach in this series at first we will
discuss commands and then I'll show you
how to use those commands and where
programs now some of you might be
wondering what is so special about shell
programming and why do we have to use it
now there are a lot of advantages that
shell programming offers over other
programming languages and some of them
are that it's fairly very convenient and
easy to build programs using shell
scripting and it's even more convenient
to debug them and also there are
thousands and thousands of building
programs that you can use and that makes
your work easier and if there is a
complicated asset that you have to
perform then you can you know do it in
very little time using shell programming
and there are lot of other advantages
that it offers and you know some of
those advantages you will figure out
figure out on your own as we progress in
this course for the time being just hold
my word you're not wasting your time
here now what is a shell a shell is
basically an interface that I interface
between us and the UNIX kernel what the
job of the shell is if we have to get
some tasks done for example if you have
to get a document printed then we issue
a command to the shell and the shell
interprets that command and translate
said into something that the kernel can
understand the UNIX kernel is basically
a program that manages the system's
resources or the hardware so what the
kernels job in this case would be it
would take the instruction from the
shell and it would further translate it
into a language that the printer can
understand and thus it would get our job
done so if we have to get something done
we instruct the shell to
to instruct the colonel to actually
execute whatever we wish to do now how
do we access the shell the shell is
access to an application known as the
terminal in window you can find terminal
in the applications category in the task
bar at the top now it's right here in
the accessory section now what I have
done is I have created an icon on my
taskbar now this is because I use a
terminal a lot and you know it doesn't
make any sense if you don't have an icon
either on the desktop or on the taskbar
and if you have to go to applications
and then search for terminal each time
you have to access it so what you can do
is you can either create an icon on the
taskbar or you can simply drag and drop
the terminal on the desktop now what
happens when you open the terminal let
me just do that for you
I'll maximize it now I see some text
being displayed on my screen this is
something that we understand later for
the timing app I just clear the screen
field I see this statement of being
displayed I'll I you know just take a
minute and talk about this mother here
is my username right and Ubuntu is the
name of my machine now you know this is
something that you input when you're
installing the operating system you know
at one of the stages the Installer asks
you to provide a name to your machine
and if you call it open through then
this is what use that you know I mean
this is something that you know comes
from there and immediately after open -
I see a dollar symbol now this Torah
symbol represents my shell this is
basically the symbol of my shell and the
cursor that's blinking after it is
basically the place where I can type in
commands and if I press ENTER then my
command gets executed now one important
thing that you all have to keep in mind
is that all Unix commands are input in
lowercase alphabets if you type in a
command in uppercase letters then it
simply won't execute I can demonstrate
it for you guys for example
we just first type in some commands that
do not very exist now these are commands
not found so I have just created some
garbage on my screen now in order to
clear this I have to use the command
clear which is Cle AR now I have pressed
the caps lock key on and if I press
ENTER it tells me that clear is a
command not found a switch caps lock off
and I'll type in clear and press ENTER
and you see that my terminal has been
cleared so this is something very
important and you must remember it you
have to input all Unix commands in
lowercase letters now in this tutorial
we are going to discuss a couple of
commands what if I want to know the time
at which I logged in the command for
that is Who am I I simply type in who
space am and space I and press Enter at
the terminal and I would see this thread
the first column displays my username
the second column displays my terminal
ID and the third column displays the
time and date when I logged in so this
is the first command Who am I you can
make a note of it the second command
that we are going to check out is PWD
PWD stands for present working directory
and it basically tells you the directory
in which the shell is currently in now
I'll elaborate on that in the future
tutorials but for the time being you
know just know that the shell uses a
particular directory
directory to do stuff for example if I
would execute mkdir or the create diary
command here then you know my directory
would be created in my present working
directory
unless of course I specify a different
path so that is it when I type in PWD
and press Enter
I see that my home folder is currently
my present directory now the home folder
can be found in the file system if you
click on places and then if you click on
home folder this is basically my home
folder and you can see the contents of
the home folder here
now I can view the contents of my home
folders from the terminal using the LS
command but we are not going to discuss
LS in this tutorial since we're running
out of time that I will be doing in one
of the coming tutorials
so thank you thank you so much for
watching this one and I hope to see you
in the next one
please subscribe to my channel and see
you in the next tutorial