Linux - Special variables

so into our previous video already we

have seen how we can use different kind

of variables into Linux now what if I

want to see what are the predefined

variables we have into the Linux

operating systems as we know the shell

variables are also called as your

special variables so some of the

variables are by default defined into

the limits are this now if I want to

insert or get a variable details of an

argument created into a particular file

or a program I can use certain variables

where dollar 0 can be used to check the

script file name now if I have run a

script I want to check what are the name

what is the name of my current script

file I can declare dollar 0 then we have

dollar n now if suppose I want to check

this second instruction or the second

call or command given into my script

file I can give dollar and two that

means it will run only the second

command of my script file

same way we have dollar hash now it will

check for all the supplied instruction

into a script fir the third way fourth

we have that is dollar and aspirin now

it will check for the double quoted

arguments into a single individual file

itself so it will check for directly

dollar one dollar total number of

arguments you generally have in spite of

dollar astrick I can also use dollar at

the rate sign now it will individually

run for tick double quoted instructions

we generally have so it can again be

equivalent to all the particular

instructions which are ragged but it

will run it individually the next we

have that is dollar and question mom so

dollar question mark runs the exit

status of the last or the previous

script which we have run so what was the

output of the script we can check it

over here the next we have that is

taller and daughter this will check for

this script and we'll also check what is

the process which we had exactly into

that particular script which we have run

the next we have that is dollar and

exclamation the dollar and it's number

we'll check for the background command

which we are using for running those

scripts where the background commands

are those particular thing with our

script is dependent on so this are the

by default script provided by the Linux

command line it's tough and you can

describe use the scripts anywhere into

the program so that you can reduce your

complete programming scores and the

efforts you are going to add it into it

so let's see how we can use this

particular scripts into aberrant

commands and check for the output so

here we'll be creating a special or

variable file that is your message file

but I'll be adding these special

variables so for that I'll be creating a

file with name as variables that is a

special variable as far dot SH and we

are going to add a line called as echo

the name or we can also define it

directly you know I want to create a

file and then I want to list the name of

the file while I run the shell script so

for that I can define the echo friend

come on and I'm going to print current

file name first so my current nya file

name if I want to display I can use a

special variable as a dollar zero and

then I can also print the first

parameter

of a particular variable with

I just used as I know this in spite of

using my dollar that's very cool

this first parameter is so if I add

multiple values into the file so the

first word will be treated as the first

parameter and the second word will be

killed as the second parameter

so for that I'll define two same way if

I want to define for the third parameter

and go for

barometer is and then dollar three right

if we want to print all the parameters

I'll be using

by using the quartet parameters

you

or sign a trait we can use

and also we can use

the coated parameters

you

here you can use this and district

can also count the number of

you can count by giving dollar and hash

okay I want to just say to fall and we

can check here I running default I guess

s who are got SH so join me nothing

because I haven't added anything used so

to add this we have to add our variable

over here now for example I'm just going

to define if were trainer so it is going

to run the file it is running the

current name then displaying the value

of your first parameter but not in turn

second because we haven't added any

rewards here the count of parameter is

one same way if I want to define all the

parameters I can also use

you can find the second parameter is

again this plate here right and the

count of where our parameters are to

same way you can also use a soir

I got a such technical trainer

quite so you can find here the third

parameters are displayed and we have

third parameter

we can define forwards now we'll see if

we have more than four three parameter

what will happen

you

empty only we are able to three the

three parameters right here just showing

you all the coated parameters and the

count of parameter is so this is the way

how we can add the special parameters

and by using the special variables we

can get the entries what we require so

for example on the top of the page every

time you want your filename to be

displayed you can use this one can check

for the parameters or the count of

parameters you have used into the

complete file you can also get the count

of it so this is what we have seen using

a special variables so into next video I

am coming up with array of freebie

values we can add into the variables

into the next video