Shell Scripting Tutorial for Beginners 11 - Floating point math operations in bash | BC Command Video Lecture | Complete Linux Course: Become a Linux Professional - Software Development

hey guys welcome to the next video on
shell scripting tutorials for beginners
in the last video we have seen how we
can perform basic Electra Matic
operations in shell scripting now in
this video we will see how we can
perform the same automatic operations on
decimal numbers now by default the
scripting doesn't support decimal number
or thematic operations using these two
method which I have shown you in the
last video now we need to use a special
tool and there are many tools and I am
going to show you one of the tools which
are frequently used to perform automatic
operations on decimal numbers but first
I will show you what the problem with
these two method and we want to perform
the automatic operation on decimal
number so for example instead of 20 I
will just take 20 point 5 here and I
want to see the result what I get when I
perform the these addition or
subtraction or multiplication division
or modulus operations on these two
numbers right so let me run the script
and let's see what happens so you can
see we got this error that this is
invalid the automatic operator and you
know you can see these kind of errors
here right so when the value is decimal
shell scripting of the bash scripting
does not perform these are automatic
operations on those numbers here also it
says non integer argument for using
whenever you be used exp our command it
says non integer argument right so we
need to use a special tool which is
called BC BC stands for basic calculator
and most of the time it comes with your
Linux distribution right so you can just
search for BC you can do man
BC here and then press ENTER and you
will be able to see this kind of man
page of BC and by definition you can see
BC is an arbitrary precision calculator
language so it's a language in itself
for basic calculations right now if you
want to know more about this command you
can read what are the options we can use
in with BC or you know what we can do
with BC right but for now we want to do
the basic arithmetic operations so let
me clear this script and in here also we
will just remove this and for now what
we want to do is some basic arithmetic
operations let scripting so how we can
perform these operations so what we do
is we basically for example what what up
with whatever integers or decimal values
you want to perform this automatic
operations you just need to write those
integers for example I want to add
twenty point five plus five for example
and if I want to do this automatic
operation I can use a pipe symbol here
and then the BC command okay
and this basically means is whatever
come on you use on the left hand side we
are using this echo and this text on the
left hand side will be treated as an
input for the command on the right hand
side of this pipe okay so this will be
treated as an input for the BC command
okay and let's see what happens when we
run the script once again so let's run
the script once again and it gives us
the answer right it gives
twenty-five point five which is true and
we can do the different automatic
operations using this PC command
so let's perform them so for example I
want to do the subtraction I want to do
the multiplication for example and I
want to do the division and I want to do
the modulus operation and let's run the
script once again it does give the
answer of each operation so addition
gives us the right answer subtraction is
also correct you can see here
multiplication is also correct division
in the case of division you can see it
gives a give it's giving us four right
and it's not giving us the proper value
of division and I will tell you why and
I will also tell you how we can solve
this problem right but modulus operation
is giving us the correct value so we
want to solve this problem which is for
the division so to solve this problem we
need to set a variable scale for this
division operation and how we can do it
we can just write scale here so just
write scale and then we need to set the
value of scale for example we want to
have the result up to two decimal places
then we can do scale is equal to two so
scale is the value we want the decimal
places to be right so we want the two
decimal places then scale can be two you
want the 20 wrestle places then the
scale can be 20 right and once again we
run the script and you can see this time
we got the correct result so always use
the scale whenever you use the division
operation right and division operation
or scale is just our decimal point value
whatever you want so if I write here 20
decimal points or 20 as a scale and when
I run the script you can see I get the
result up to 20 decimal points right
so this is how you can use BC but BC as
you have seen in the main pages it's not
just for arithmetic operations it can do
much more than that so for example we
want to calculate the square root of
some number or if you want to do some
trigonometric operations with BC you can
do everything now we have seen as we
have done this arithmetic operations
with these decimal values but what if we
have these two you know variables and we
need to use these variables in place of
these values so to do this you can just
do like this as you do with variables so
variable number one plus dollar num -
mum - okay same you can do with other
you know other values so instead of this
you can just - - here and so on right
and let's run the script once again and
it gives us the same result
so whenever you want to use the variable
use the dollar symbol with the variable
and the arithmetic operation you want to
perform now I was talking about the
square root so how we can perform the
square root or something so say I have a
number once again I will declare a
variable num and its value is for
example I will say 27 okay and I want to
do the square root of 27 so I can just
do echo and then first of all I will set
the scale to be 2 for example so scale
is equal to 2 and then the semicolon and
then there is a function called square
root or sq RT so you just use sq RT and
then in the bracket you can use the
variable for which you want to calculate
the square root so I want to calculate
the square
of this variable or this number so I can
do something like this now after this as
you already have guessed we use BC but
alone of it BC command it will not work
because this is a math operation and to
use this math operation we need to use
the math library with this BC command
and to use this math library you just
need to write minus L for that right and
minus L for calling the math library in
which the square root function is okay
and let's run the script once again let
me clear the terminal and run the script
once again and you can see the last
value here is the square root of 27
which is correct you can do the square
root of 27 and you will get this result
right for example I want to do the
square root of 4 and I want to run the
script once again you can see the result
is 2 which is easier to understand right
now for example I want to perform for
example I want to get the power of 4
something so something to the power of
something how we can get it so for this
we just need to use whatever integer I
have so for example I want to get 3 to
the power 3 I can write 3 and then this
symbol I don't know what we call the
symbol for example cap symbol and then 3
ok
so this means to the power okay so 3 to
the power 3 and once again we can run
the script and it gives us 27 which is
correct 3 to the power 3 is 27 so there
are many math operations you can perform
the width BC and you can do a man BC for
reference so you can give this command
and you can go little bit down so you
can see for calling the math library
which we have used here we use minus L
Flags is for interactive mode
W is for warning as is for standard q is
for quit whenever we run the BC command
on terminal this is handy command to
quit out of the BC command and then V is
for version and then when I scroll a
little bit down I can see what are the
operation I can do with the BC command
so I can do post increment or pre
increment you can see here
multiplication and subtraction division
modular of operation and you can see
this is for calculating ^ something
right and then we have other operations
here also so comparison also you can do
with BC commands and all the logical
operations you can do and we have called
this function or method which is used to
calculate the square root which is this
one right so you can read this man page
and you can see what are the things you
can do with BC come on so just to man BC
and you will be good to go so I hope
you've enjoyed this video please like
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