Shell Scripting Tutorial for Beginners 12 - The case statement 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 learn how to use
case statement in scripting so the case
statement is good alternate for
multi-level if-then-else condition or
statements it enables us to match
several values against one value now
what is the basic syntax for a case
statement so let me show you the basic
syntax for case statement so this is the
basic syntax for case statement you use
the keyword case and then you give any
expression to evaluate right this can be
a variable name or any expression to
evaluate then you will give the keyword
in and then you match multiple patterns
so you can have multiple cases to
evaluate so you can use a pattern here
it can be a strict pattern or flexible
pattern like regular expression and then
you use this parent is closing
parentheses to show that this is the end
of this case and then comes the
statement after this case so if the case
is true then the statement is executed
and then this double semicolon indicates
the script that this case statement has
been finished so start using the second
case or start evaluating the second case
right and with the second case also you
can use a statement and then the third
case comes and fourth case and then all
the case comes and at the end you have
this e sack or the reverse of case so
from right hand side you can seek CAS e
but it's the reverse of for this case
spelling right so
how you can use that case let's take an
example and let's see how we can you
know actually use the case statement in
real life so let's say we want to
evaluate a rental of some vehicle so to
that for example I will just take an
argument with the script so I will take
an argument with the script when I run
the script and this argument I will save
in for example in a variable and
variable name I will name it as a
vehicle is equal to and then the fourth
argument which is passed using the
script I will just pass it to the
variable vehicle ok and then I will
evaluate this vehicle so this expression
comes here and it can be variable also
so you can just evaluate this vehicle
here so case and then dollar symbol and
then the name of the variable which
contains the name of the vehicle or type
of the weaker and then this in and then
comes the pattern okay so for now we
will just see the strict pattern here or
compare the strict pattern so if this
vehicle is for example car we will just
execute some statement for example we
will echo that the rent of this car is
something so let's say we will print
went off for the vehicles in our case
which is car is $100 for example right
in the similar manner you can echo
second statement so if the vehicle is
for example van then we will see a rent
of the van is $80 right and in the same
way we can add multiple pattern matching
here so let me add one more pattern for
example we will get the input
bicycle so bicycle rent is for example
$20 or let's say $5 okay and let's say
user input truck so the rent of the
truck is one $50 for example right and
if the user inputs the any adult value
other than these four values we want to
catch this value which is a random value
for example and this random value you
can catch from star and then this
parentheses okay now this asterisk means
if you know Linux command line aspects
means a wild-card which matches any text
okay so in the default case this case
will be followed and then we will say
here we will echo here that this vehicle
is unknown and we will just say the
vehicle is unknown okay this is a
default condition right so let's run the
script and let's see what happens when
we run the script so and then I will
just run this script and it says unknown
vehicle because I haven't given any
argument with this script and this
script expect that the first argument
which is passed with the script is the
vehicle type right so let's run the
script once again so let's say we enter
car with this tent so the script name
and the argument is car and you can see
rent of the car is $100 right so this
condition all expression is met so it
echoes this statement right earlier we
haven't given any argument here so it
goes to the default case which is this
case which is unknown vehicle right
let's give some other case for example
van and this time
the van is $80 for example let's say we
enter
clock and this time the rent is one $50
for the truck right so in this way you
can do the pattern matching and in this
way you can use the case statement in
scripting but here the pattern matching
can be anything so right now we are
matching the strict pattern so we are
just matching whatever is entered using
this argument but this can be anything
so this case can be any regular
expression or any pattern which you want
to match so if you want to match some
pattern you can do it also in this case
and if you don't know what is pattern
and how to use pattern just search for
regular expression I think and you will
have the good idea about pattern
matching and you know regular
expressions also ok so this is just one
example of using case statement in the
next video I will take one more example
of using case statement and we will
consolidate our knowledge on case
statements so stay tuned and please
would come and subscribe and bye for now