Shell Scripting Tutorial for Beginners 24 - Local variables Video Lecture | Complete Linux Course: Become a Linux Professional - Software Development

hey guys welcome to the next video on
shell scripting tutorial for beginners
and in this video we will talk about
local variables now by default every
variable which you declare in your
script is a global variable and that
means it can be accessed from anywhere
in your script now let me give you an
example and then we will understand why
do we need a local variable and how to
use them so this print function I have
shown you in the last video that you can
declare a function like this and this is
a function print which takes an argument
and whenever we provide an argument for
example we call this print function like
this and we provide the first argument
this way it will be assigned to this
dollar one we have seen in the last
video right now let's say this function
we need to use to print a name so I'm
going to declare a variable called name
here and I'm going to assign the value
of for this first argument like this
here and here we will just print the
value of the name right so we can just
write the name is and then the variable
name which is dollar name here right and
let's run the script and let's give some
name here so print for example the name
is Max here right so I'm going to just
run the script and let's see what
happens so it prints the name is Max
which is correct right because this name
is assigned to this variable and then
this first argument is assigned to the
variable name and we are printing the
value of name now I said previously that
all variables are global in shell script
so the name can be declared here also
and then we can assign some value to it
so let's say now we assign our name of
where value Tom to this name variable
right and then we can just write echo
here and then we can just say
the name is and once again dollar name
right so let's run the script once again
now and let's see what happens so first
it says the name is Tom because we have
assigned the value of a name first of
all Tom so this is the function
declaration right and until and unless
did you call a function it will sit like
this right so the shell script execution
start from here right and we declare a
variable called name and then we assign
some value to it which is Tom here and
then first of all we are printing the
value of a name which is we which is
assigned to the name so it will print it
will be printed from this echo command
and then our print function will be
called and then using this name variable
this echo command will be executed which
is printing the second line of code
which is the name is Max and then our
default echo value which is foo is
printed here right so what it tells us
that this name is a global variable and
we can access it from anywhere in the
script but sometimes we want that our
variable which we define in a function
should remain a local variable so it
should not be changed
outside of the function and that's where
the local command comes in so there is a
command called local and whenever you
add this command then your local
variable your variable becomes local and
it can be used inside a function only
right so we can just declare this
variable name something like this and
then we can say local we add a local
keyboard before it so let me just remove
this local keyword for now and let me
add once again the name is here so I'm
printing the name is after the print
function is called and before the print
function is called right so I will just
say the name is this and then we can
just write colon before and colon after
right and let's see what happens here
before adding the local keyword right so
I'm going to just run the script once
again and you can see that once again
the Tom value is assigned to the name so
before this function is called the value
which is assigned to name is Tom which
is correct but after this function print
is called now the value max is assigned
to the name variable now so it prints
the name is max from diff echo command
and here this command prints the value
the name is max once again so the you
know variable which is name now
possesses the value max right so this is
little bit confusing right because our
we expect that this should remain Tom
because this is outside our function
right so this name is local to this
function and we expect that it should
not change the value of this global name
right so here we want the name is Tom
because originally this is a global
variable and we have assigned the value
of Tom here and after this function is
called we expect this this variable
possess the value Tom and not max but
what's happening here after this
function is called the value Max is
assigned to this and
and then it's printing the max name here
using this echo command which we don't
want and that's why we use the local
variable for example we just write
locally here and once again when we call
the script or run the script now see
what happens so now whenever you add
this keyword local in front of your
variable then your variable is local to
this function and it cannot be accessed
outside the function so this is just a
local execution of codes and it will not
affect the global variable so now what
happens we are in this variable name is
different from the this variable local
name right so first of all we have
assigned the value term to the name and
it will print the name is Tom using this
before right so this is the echo command
which is printing the name is Tom here
then we are calling the print function I
print the name is Max here because we
have assigned the value to this local
variable Max but not the global variable
name right so it prints the name is max
but once again when we call our name
variable then it prints the name is Tom
once again which we are expect right so
this global variable is now different
from this local variable because this
local variable is you know only
accessible by this print function not
from somewhere else from this script so
this is how you can use local variables
and this is the concept behind using the
local variable so I hope you understood
the basic concept I hope you enjoyed
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