Shell Scripting Tutorial for Beginners 14 - Array 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
in this video we will see how we can use
arrays in shell scripting now bash
suppose simple one-dimensional arrays
and to declare arrays you just need to
use the name of the array so whatever
name you want to give to your array
variable just give it for example you
want to have operated system array
variables so I will just write OS is
equal to this is the name of the array o
X right and then you just use this
parent ever and in the single quotes you
just add the element to the array so for
example I will just add Ubuntu here and
then separate it by a space no comma you
just need to add things a second the
elements for example windows and so on
so third for example we will add Kali
Linux or Kali right and just save it and
to print this array you just need to use
echo and I think in the first few videos
we have seen how we can print array but
we will repeat this thing so just use
dollar symbol and then in the curly
bracket name of the array or a name is
OS and then in the square bracket use
the special character at the rate which
is going to print the elements of the
array so let's run the script and let's
see what happens so you can see it
prints the elements of the array right
now in order to print any specific
element you just need to use echo and
once again dollar symbol curly brackets
name of the array and the square bracket
the index of the element which you want
to print so for example I want to print
Windows which is the first element and
how it's the first element or for the
first index the
element or index of the array starts
from the 0th position so this is the
index 0 this is the index 1 and this is
at the index 2 right
so index 1 is assigned to the windows
element right so let's run the script
once again and let's see what happens so
it prints windows if you right here 0th
index it's going to print ubuntu right
and let's go ahead and i'm going to show
you how you can print the indexes or
indices of the array so you just need to
use once again the dollar symbol and the
curly bracket and the name of the array
and once again in the square bracket use
the add the rate but this time here you
just need to use not symbol this
exclamation mark okay and let's see what
happens when we run the script and you
can see it trains the indexes of the
array or indices of the array right so
we have 3 element which starts from 0 1
2 so it prints 0 1 2 ok now for example
you want to print the length of the
array what we will do we will just write
echo and once again echo and then the
dollar symbol once again and then the
square bracket name of the array and in
the square bracket you just need to
write at the rate special character and
in front of the array variable name you
just need to add this hash symbol okay
and this means you want to print the
length of the array okay so let's run
the script and let's see what happens so
you can see the array length in our case
is 3 because it contains 3 elements
right now how we can add elements to the
array so to add elements
you just need to write the name of the
array and then whatever index at
whatever index you want to add an
element you just need to write the index
of that element so for example I want to
add at the index 3 some other OS name so
for example I want to write Mac here
okay so this will be added to the third
index of this array now let's see what
happens when we run the script you can
see here this fourth element is added to
an array at the index three right so in
this way you can add the element now if
you want to update this so for example I
right here at the 0th index then this
Mac will be assigned at the 0th index
which is going to replace this ubuntu by
Mac right so let's run the script and
you can see now it has at the 0th index
Mac then Windows then Kali okay so if
you want to update it you just need to
write the index of the element which you
want to replace the new element with and
then you just assign the element value
okay now we will see how we are going to
remove how can we remove element from an
array so to remove an element from an
array what we will do we will use the
keyword unset so just write unset and
then the name of the array so money
array name is where and then whatever
index of the element you want to remove
so for example I want to remove the
index at which Kali Linux is let me just
edit this index also so Mac is at the
third index right and Kali is at the
second index so 0 1 2 ok so I am going
to remove
the callee from my array right so just
write the index value of the element
which you want to remove and then once
again run the script and you can see now
we have open to Windows and Mac and no
Colleen right now you may ask why it's
printing like this because we already
have removed the element at index two
right so it's like that that in bash
you can add element at any index so it
can be for example at fixed index and
nothing is going to happen it's going to
print the elements of the array in the
sequence of the index right so if it
it's at the fixed index it will be
sorted in the ascending order so 0 1 and
then if it it it is at the 6th position
or index and it's going to just print
the value at the fixed index and now
this position will be ignored so this
means that some members of the array can
be left uninitialized and gaps in the
arrays are okay now bash permits arrays
operation on variables also even if the
variables are not explicitly declared as
an arrays so let's take an example so I
have a variable name called string for
example and I assign any value to it so
let's say this random string right
now when I I will just take this echo
come on here and then I will just print
the string right string array and let's
see what happens so let me clear the
terminal and let's run the script once
again and you can see here it prints the
you know array or string value as it is
right so you can see string is printed
right so
taking this string as an array so you
can use this kind of notation also but
let's print for example the 0th index of
the array so once again I'm going to
just write 0 here instead of at the rate
I will just write 0 and then once again
run the script and it prints the same
string value right let me just print the
index 1 value and here the magic happens
you can see at index 1 there is nothing
so why this is happening because you are
going to treat any variable as an array
the array element value at 0 10 Dex
whatever the value of the variable it's
assigned at the 0th index right so you
can treat any variable as an array but
the value of this array will be assigned
to the 0th index okay so at the first
index there is nothing because the whole
value is assigned to the 0th index and
this we can prove by printing the length
of the array also so let's print the
length of this string array and let's
see what happens so you can see the
length of the string array is only 1
which is this one ok so this is how you
can use arrays in bash scripting I hope
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