Linux -Shell function

now here in this video we are going to

talk about these shell functions by the

name itself functional means we are

going to process something so as been by

default in Linux you have multiple

functions which are inbuilt into the

shell itself now if I'm going to use

those functions this will be a very big

functions which I cannot use completely

at a time or if I don't want to use the

whole function at a time what I can do I

can break down those functions into

multiple parts that's what we are going

to look over here so now you can see

shell functions generally enable you to

break down any particular functionality

which we generally have into a shell

into a smaller logical subsections and

this subsections can be used to perform

any particular task individually when it

is required by the user or the system so

this the function is now here we are

going to see what are the types of

functions we have as well as what are we

shell and what are the functions can do

into your programs so very first thing

you can also create a new function if

suppose I do not want to use the

existing functions I can call so create

my own function a smaller function to

perform a task also we have the passed

parameters of this function now

functions we can also pass multiple

parameters multiple options we can set

into the functions or the existing

functions we have we can also return the

value to the functions now returning

value again we have seen into the loop

how we can return the value into the

loop same kind of return values we are

going to add also in the functions then

we are going to create nested functions

we are going to add a new functions into

the existing functions this way we can

also create a nested functions as we

have used into the if-else value same

wave functions can call from the prompt

itself so this functions like already

have created the function and wherever

in any of the terminal if you want to

call this particular function so to

perform your tasks you can call it so

let us see how we can create the

function and how we can use it into our

prompt of your shell so again I'm going

to create a function in a shell itself

shell script itself so I'm going to

create

- as such and now fortifying the

function what you need to do is you need

to define a name of the function now for

example I'm defining the name as hello

so I want to create a function with name

hello so for that you need to define in

such a way that you are going to call

this hello and you are going to add into

the hello function so what you need to

add I want to add echo hello what okay

so this actually I want to add for

adding it again we need to do one thing

that is we'll just add a curly braces

over here that we are going to start

adding something into it right either

here or at the starting generally see

you can add anywhere but if you line it

well so you won't have any particular

confusion while you are writing any

particular script or any particular

functions so once you have address with

that I need to close the braces once you

have closed the presses just hit enter

and again here itself you can also

invoke here

function hello so then walk hello

function so we can give the command only

hello so automatically it will get

involved let us check as such function

dot Sh

so it does invoke and you got the value

as hello world so this is how then

really you create a small functions into

your Linux operating systems now again

you can also add the variables into the

functions like if I want to call a

particular variables I can also call it

like I will just define like we have

already used in to our previous example

I I am going to call the parameters like

so we have seen how we can call the

parameter that is first parameter and

your second parameter I'll just save it

I just gave as such function dot Sh

trainer or I can say

technical trainer hit enter Nagin's it

is calling booty

just a sec I we need to check it to show

us body parameters as well

you

okay so haven't we need to do is like

you know we are getting going to move

into the function door as such itself

and in spite of invoking it you know

from outside I'll just invoke it from

here itself okay so what the output you

should get so I'm just going to define

the parameters over here itself they

technical

hit enter save it read it out as such

functions are as trade will show you

hello wall to it first parameter and we

can see if these second parameters over

here if you can add multiple parameters

you can also add multiple parameters and

you can call it over here itself so this

is the function which we have seen now

again we can also return the value into

the functions so for that what we can do

is we are going to just capture the last

command and return the value to it so

for that what I am going to do I will

just move into the function dot SH come

on I just

capture

the value return or returned by last

command and now return the value so for

returning the value I'm just going to

add one of my characters sure that has

any particular value any particular

special director's if you have or if any

particular you know variables you have

so it should fetch those particular

thing and then we'll be using echo

command echo returning

to return value so return value I will

be using by using the variable which I

have defined here that is body T once

you have done with that close it and hit

enter

save it save the file

yes tell go and check for this file so

you can say there's no returning the

value T 0 because we haven't got any

particular or potential you know you can

also define the numbers we can also

define three-ton values now if I want to

define the return values what you can do

is move into the function again okay

just me find the return values here

under the echo command which you have

defined into the function I'm going to

return the value 210 return J once you

have done with that save it as such

functions done that's it so I can see

the return value you have that is 10 so

if you have certainly done value it will

directly take you know the return value

if you haven't set anything it will

directly move on to the value 0 from the

last output after the last output we can

see so this is how we can return your

values to another value same way if in a

function if I want to call multiple

function so I'm going to create multiple

functions into our same file and I'm

going to call one function from the

other function so for that I'm going to

again create a file which is no multi

function file mmm function this is the

name I am going to define and this is

the H file I'm going to create and now

I'm going to create a functions by

calling one function to another function

it's right another function so very

first function I'm going to define which

I am going to call from the another

function so that I am going to define

the first

function

which will be called from the second

function so this we can define so I have

to combine check it out so I'm going to

define the function 1

okay and I'm going to start with the

function as we have that to the previous

function I'm going to use the brackets

into the brackets I need to define our

open D bracket here and post that I will

add the first function the description

of it this is the

first function okay done with that enter

it and you can define the other function

so this is the calling function we can

say like I want to call the other

function

the second function I can see so here

I'm going to call the second function

which I'm going to create later on so

I'll define the second function by a

named function - so I'll be defining the

name of the function as function - once

you have done with this I'm just going

to close the bracket here so this is

completely closed then I'm going to

define the function

so you should be you know very

particular about the name because you

have used this particular name here so

function - I'm going to define and do

that again I'm going to start with the

know and drink the echo command into it

and I'm going to add this second

function so once you have done with that

again I'm going to close this so you're

gonna have I know close the second

function and I'm going to call

function1 right so for that I'll use

function one so I'll just invoke this so

if we are invoking it you over here

itself so hit enter and give command

multi pal function shell so you can see

you have two different functions okay so

our function one was not called okay so

once the function once has been called

so it is again showing you a different

function so just showing you body

functions because your function one has

already called your function to write so

what we have done is we have you know

function one and function 2 we have

defined now I have just called a

function to from the function one and I

have run just function one so

automatically or function two is been

run now if suppose I remove this can

also remove it

if I do not call it from the function

one right and if I give come on

same and function it will show me only

first function which is running right

now never warned what the function

should be working together so I'll which

is defining the functions now for

example again I want to

for example I'm going to call function

- from function1

and again the function one is calling

your function

now let's check the entries there both

are calling each other

Chansey now this will create a loop

right so this kind of cases should not

happen if it has happened we have to

define our break statements so this will

form a loop unless we are going to

control this particular loop so it won't

be happening it so so both the loops are

calling each other and they are like you

know going on creating their loops into

it

so always avoid doing this like I will

be just defining one function here and

unless I have removed it

I just remember one of the line from

here okay done now again if I run this

thing it will work well right it has

quality turning value so this is we will

just run the multi functions so now here

we can see the second value or the

second function is again well it over

here so this is how generally we create

the functions this is how generally be

you know create a functions and call the

other functions into the existing

functions as well so here we have talked

about all the functions which we have

seen and you know how we can create the

functions and as your even the machine

or your Linux operating system has some

built-in power functions they are like

exp which we generally use they are

dependent functions even we use your abs

which is a built-in function so do we

have lot of built-in functions into the

machine so by default your system calls

then when it is required so here we have

talked much about your functions and

then we are going to see something about

the administration and how to get help

for the different commands which we have

used into the next weight here so keep

watching