Mark a variable or function as read-only.
Syntax
readonly [-apf] [name[=word] ...]
Key
-a Restrict the variables to arrays
-p Display output in a format that may be reused as input
-f Mark functions corresponding to the names as read-only
The given names are marked readonly; the values of these names may not be changed by subsequent assignment.
If no name arguments are given,or if the -p option is supplied, a list of all readonly names is printed.
If a variable name is followed by =word, the value of the variable is set to word.
The return status is 0 unless an
invalid option is encountered, one of the names is not a valid shell variable name, or -f is supplied with a name that is not a function.
readonly is a bash builtin command.
Related:
set - Set a shell variable = value
