Unset Variable:
The shell built-in unset command is used for unsetting the data that an initialized variable is holding.
Syntax: unset <Variable Name>
Example: unset name
The above example will unset the data for the variable name is holding.
Readonly Variable:
The shell allows to mark variables as readonly; once the value is marked as readonly it cannot be charged
Syntax: readonly <Variable Name>
Example: readonly name
The above example will set the variable “name” as readonly
$ name = “Ram”
$ readonly name
$ echo $name
Ram
$ unset name
ksh: unset: warning: name: is readonly