Korn Shell: Unix and Linux Programming Manual, Third Edition, The

The readonly Command

The readonly command sets the value and/or readonly attribute of variables. It is equivalent to the typeset –r command, except that when used within a function, a local variable is not created. This command sets X to readonly and assigns it a value of 1:

					$ readonly X=1
				

This is equivalent to:

					$ typeset —r X=1
				

Multiple variables can be given to the readonly command.

					$ readonly X Y=1 Z=2
				

If no arguments are given, a list of readonly variables and their values is displayed:

					$ readonly
					Z=1
					Y=1
					Z=2
					PPID=175