Variables

 Defining Variables

variable_name = <variable data>

num="1"

name="Devil"

Accessing variable

Variable data could be accessed by appending the variable name with ‘$’ as follows:

#!/bin/bash

VAR_1="Devil"

VAR_2="OWL"

echo "$VAR_1$VAR_2"

Unsetting Variables

The unset command directs a shell to delete a variable and its stored data from list of variables. It can be used as follows:

#!/bin/bash

var1="Devil"

var2=23

echo $var1 $var2

unset var1

echo $var1 $var2

Note: The unset command could not be used to unset read-only variables.

Read only Variables.

These variables are read only i.e., their values could not be modified later in the script. Following is an example:

#!/bin/bash

var1="Devil"

var2=23

readonly var1

echo $var1 $var2

var1=23

echo $var1 $var2

Now let us see all the above codes in action together. Following is a shell script that includes all the shell variables discussed above

# accessing the declared variables using $

echo "Name is $Var_name, and age is $Var_age."

# read-only variables

var_blood_group="O-"

readonly var_blood_group

echo "Blood group is $var_blood_group and read only."

echo "Error for read only variables, if trying to \

modify them."

echo

var_blood_group="B+"

echo

# unsetting variables

unset Var_age

echo "After unsetting var_age..."

echo

echo "Name is $Var_name, blood group is $var_blood_group\

 and age is $Var_age..."