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2.3 Read-Only User VariablesThe contents of the user variables and the shell variables can be modified by the user. It is possible to assign a new value to them. The new value can be assigned from the dollar ($) prompt or from inside a BourneShell script. Read-only variables are different. The value of read-only variables can not be changed. The variable must be initialized to some value; and then, by entering the following command, it can be made read only.
Command format: readonly variable_name variable_name = name of the variable to be made read only
Command format: expr expression See Appendix C for a complete list of expressions