Add a (name, value) pair to a line based file, or update an existing (name, value) pair.
file: The path to a line based file
option-name: The name in a (name, value) pair
option-value: The value in a (name, value) pair
--separator: Characters which separate the name from the value in a (name, value) pair.
--compare-values: Prevent duplicate lines as normal, but compare the contents of the "value" field instead of the "name" field.
--check: Do not actually make any changes, but report whether or not a change would be made.