Shell Scripting Tutorial for Beginners 21 - Select loop 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 to use
select loop in shell scripting now first
of all why he use select loop so the
select construct allows us to generate
easy menus so whenever you need to write
a script which requires some menus then
you can use select loop now let's see
the basic syntax of select loop so to
use select you just need to write this
select keyword and then you need to give
any variable name and then this keyword
in and then you can give a list of items
here and then in do and done in between
do and done keywords you can execute
some command based upon the list you
have provided so let's see actually how
we use select loop so for example I have
the list of some names so I'm going to
declare a name variable here and the
list can be some names so for example
mark John Tom Ben and so on right so
right now I'm just using four names and
then I can just print those names like
this so I can just write echo and then
selected name is whatever is selected so
dollar and the name which is this
variable right and then we can write
selected okay and I'm going to just save
my script and I'm going to run this
script and let's see what happens so I'm
going to just press ENTER and you see
here it gives us these list of names as
a menu so every name is given and before
every name
we have a number provided to us right
so whatever list you will give here it
will be presented like this with a
number before it in a sequence and then
the prompt will ask you to give any
number from this list so for example one
is associated to mark two is associated
to John three is associated to Tom and
four is associated to Ben so when I
write two and then press Enter it prints
John selected right because we selected
the second item which is associated to
John right and this is the easy usage of
the Select loop so select loop construct
is similar to follow but what it does is
first of all it iterate over the list
and give you this kind of menu structure
to us and then we can select any of the
items from the menu and then execute
some commands or statement based upon
the selected value right now select loop
is often used with the case statement so
some kind of cases can be used with the
Select loop and we will see how we can
use it so what I'm going to do is first
of all I'm going to give the basic
structure of cases so case and e-s-a see
right this is the basic construct and
then we can add some you know cases here
right so what we want to do here is we
will just see what is the name provided
so let's just use this dollar symbol and
name variable and then in we already
know what is the basic syntax of this
case statement right and
then we can just give names from this
list so whenever mark is selected then
we can print something right so just
give this and then in this case what we
can do is we can echo for example mark
selected write something like this and
then to end you can just give double
semicolon like this okay so similarly we
will just give multiple cases here for
the four names
and you can even provide the default
case here so if you want to provide
default case you can just write this
kind of syntax as the default case right
so in this case we will just echo and
then we can just print error and we can
also say please provide a number between
one to four so we can just say please
provide the number between one to four
right so you can just write this in the
case of any of the default cases which
is not present in this case list and
let's run the script once again so you
can see whenever you you know select or
give any number it's not going to you
know exit out of this menu you can give
multiple two times the number and it's
going to once again ask you the number
so in order to exit the script you just
need to press ctrl C in order to exit
out of this script right and then once
again run the script and you have these
numbers once again and then once again
when I give one it says mark selected to
John selected three Tom selected an for
been selected right
so this select loop is often used with
this case statement I am just giving you
this kind of echo statement here but you
can execute any complex logic based upon
the selected value from the Select loop
ok so this is the basic usage of select
loop in shell scripting I hope you've
enjoyed this video please recommend
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