Update README.md

Author: Tomy2e

README.md

@@ -1 +1,24 @@
-# ovh-dynhost-updater
+# ovh-dynhost-updater
+
+A tool to automatically update an OVH DynHost record with your public IP address.
+
+It can be run as a long running process (daemon) or as a regular cronjob task.
+
+## Usage
+
+### Options
+
+The tool accepts the following command-line options:
+
+| Name      | Description                                                                   | Default value |
+| --------- | ----------------------------------------------------------------------------- | ------------- |
+| -daemon   | Run the program as a daemon.                                                  | `false`       |
+| -delay    | If the program is run as a daemon, number of minutes to wait between updates. | `10`          |
+| -hostname | Hostname of the DynHost record to update.                                     |               |
+
+The tool reads the following environment variables:
+
+| Name     | Description                                                                       | Default value |
+| -------- | --------------------------------------------------------------------------------- | ------------- |
+| LOGIN    | DynHost login. The tool will exit if this environment variable is not defined.    |               |
+| PASSWORD | DynHost password. The tool will exit if this environment variable is not defined. |               |