builtin help readonly

[shoebill]

readonly: readonly [-aAf] [name[=value] ...] or readonly -p
    Mark shell variables as unchangeable.

    Mark each NAME as read-only; the values of these NAMEs may not be
    changed by subsequent assignment.  If VALUE is supplied, assign VALUE
    before marking as read-only.

    Options:
      -a        refer to indexed array variables
      -A        refer to associative array variables
      -f        refer to shell functions
      -p        display a list of all readonly variables or functions, depending on
            whether or not the -f option is given

    An argument of `--' disables further option processing.

    Exit Status:
    Returns success unless an invalid option is given or NAME is invalid.