# readonly > Create or modify read-only variables within a shell script, preventing the variable from being changed by subsequent commands. > This is useful when you want to ensure that a variable retains a constant value throughout the execution of a script. > More information: . - Create a read-only variable: `readonly {{variable_name}}={{value}}` - Mark a variable as read-only: `readonly {{existing_variable}}` - [p]rint to the standard output the names and values of all read-only variables: `readonly -p`