Updated README

README.md

@@ -14,6 +14,38 @@ Details
 
 On startup the `RadLine.dll` replaces the `ReadConsole` function with its own. This allows it to intercept the command line completion behaviour.
 
+Command line completion
+=======================
+
+This was the main reason for creating this utility. Completion is looked up using the lua script [RadLine.lua](RadLine.lua).
+The function `FindPotential` is called with the current command line and returns an array of potential matches.
+The matches are then listed under the current line.
+
+Auto terminate batch file
+=========================
+
+To enable:
+
+```
+set RADLINE_AUTO_TERMINATE_BATCH=1
+```
+
+This setting will auto respond `y` to the `Terminate batch job (Y/N)?` prompt.
+
+Post command execution
+======================
+
+The contents of the environment variable `RADLINE_POST` are appended to the current command.
+
+Dynamic environment variables
+=============================
+
+`__PID__` will show the process id of the cmd process.
+
+`PROMPT` environment variables in the prompt variable will also be expanded.
+
+`set foo=%(cmd /c echo bar)%` the command in the brackets will expand to the output of the command.
+
 Install
 =======