Shell Scripting Tutorial for Beginners 10 - Perform arithmetic operations Video Lecture | Complete Linux Course: Become a Linux Professional - Software Development

hey guys welcome to the next video on a
shelf scripting tutorial for beginners
in this video we will learn how to
perform arithmetic operations in shell
script so let's get started so to
perform arithmetic operations you may
you know consider using something like
this so you can echo and then you can do
one plus one but by default echo command
takes anything which is written after
this echo command as a string so if you
run this script you will see it will
just dump whatever which is written
after the psycho command as it is so
it's not performing any automatic
operation so how do we achieve it so
let's take an example and then we will
see how do we do it so I will create two
variable num one is equal to 20 for
example and number two is equal to five
for example okay and then I want to
perform some basic mathematics on these
integer numbers for example addition
subtraction or multiplication division
or modulus operation so to perform this
you take this number as it is and then
for example I want to do addition I can
just - num - something like this
addition is done like this only but for
this you just need to enclose these two
variables inside double brackets so you
just need to do double bracket this side
and double bracket on the other side of
this expression like this okay but still
you will not be able to achieve your
goal so if you do echo still it will
print as it is but when you do this
dollar symbol or when you add this
dollar symbols before your expression
this double parentheses expression then
let's see what happens and don't forget
to give the space here okay and let's
run the script and let's see what
happens so you can see it has performed
the automatic addition on these two
variables right so to perform these
basic arithmetic operations you need
these double to parentheses and then
this dollar symbol before them so they
could be evaluated as an automatic
operation right in a similar way we can
perform other automatic operations for
example if you want to do subtraction
you can do something like this if you
want to do multiplication we use
asterisk or star whatever you want to
call it and then for division you just
need to give this forward slash here and
there is one more operation which is
also considered to be a basic automatic
operation which is this modulus
operation so let's see what happens so
when we run the script one by one we
will evaluate all the expressions so
what's happening here is in the first
echo command we are doing the addition
which is 25 which is 20 plus 5 25 which
is true then the subtraction which is
also true you can see here then the
multiple multiplication 20 in x 5 is 100
which is also true and then we have done
the division which is also true and then
we have done the model large modulus
operation so modulus operation means
that whatever you get as a remainder
after dividing the number that remainder
will be you know treated as a result
okay in our case there is no remainder
when we divide 5 by 20 so we get 0 here
but if you use for example 21 here then
you will get one as a remainder because
five will be divided by 21 when it's
divided by 21 we get the remainder of
one
okay so this is how you perform the
basic automatic operations in scripting
now there is an alternate way of
performing automatic operations on your
integers and that is by using expr
command so to use exp our command we are
going to use the same variable but you
use only one parenthesis like this here
so just use one parenthesis like this
and instead of using double brackets or
parenthesis you just need our keyword
expr okay so you just need to use expr
and then for the variables you just need
to use them as a normal variable with a
dollar symbol something like this so use
this kind of a dollar symbol before
every you know variable so I'm going to
just use this dollar symbol before every
variable and this expr command before
these operations something like this
okay and let's run the script once again
and let's see what happens
and you can see it's giving us the
result but for the multiplication is
giving us the error and this says it's a
syntax error because in whenever you are
using expr this Asterix is not escaped
okay so you need to use this Asterix
with this escape character which is
backslash and then everything will be
okay so once again when you run the
script you will see the same result as
you got with the expression
the double parentheses but don't forget
to use this escape character before this
asterisk for multiplication whenever you
are using this expr command okay so this
is how you can do the are automatic
operation by using these two ways on
integers but what happens when you want
to perform these automatic operations on
for example decimal values this we are
going to see in the next video when I'm
going to show you how we can perform
these automatic operations on some
decimal values so stay tuned and please
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