diff --git a/doc/master/flag b/doc/master/flag
new file mode 100644
index 0000000..e04e91d
--- /dev/null
+++ b/doc/master/flag
@@ -0,0 +1,41 @@
+SYNOPSIS
+	void flag(string arg)
+
+DESCRIPTION
+	Evaluate an argument given as option '-f' to the driver.
+	If several '-f' options are given, this function will be
+	called sequentially with all given arguments.
+	This function can be used to pass the master commands via
+	arguments to the driver. This is useful when building a new
+	mudlib from scratch. It is called only when the system is
+	started.
+
+EXAMPLE
+	// The code given implements these commands:
+	//  '-fcall <ob> <fun> <arg>': call function <fun> in object <ob> with
+	//				argument <arg>.
+	//  '-fshutdown': shutdown the system immediately.
+	// Thus, starting the driver as
+	//	 'parse "-fcall foo bar Yow!" -fshutdown' would
+	// first do foo->bar("Yow!") and then shut down the system.
+
+	{
+	  string obj, fun, rest;
+
+	  if (arg == "shutdown")
+	  {
+	    shutdown();
+	    return;
+	  }
+	  if (sscanf(arg, "call %s %s %s", obj, fun, rest) >= 2)
+	  {
+	    write(obj+"->"+fun+"(\""+rest+"\") = ");
+	    write(call_other(obj, fun, rest));
+	    write("\n");
+	    return;
+	  }
+	  write("master: Unknown flag "+arg+"\n");
+	}
+
+SEE ALSO
+	master(M)