It is common for BBS door programs to accept command line parameters
that permit various door-related settings, such as the serial port, baud
rate, and node number. This tip demonstrates how you can do this when
working with OpenDoors. This tip is presented in the following files:

   cmdline.h   - Header file for command line processing function.
   cmdline.c   - Implementation of command line processing function.
   tip4.c      - Example of a program that uses the command line
		 processing function.

The cmdline.c module implements the ParseStandardCommandLine() function,
which takes as its parameters the same argc and argv parameters that are
passed to the main() function of any C program. The
ParseStandardCommandLine() function then sets the appropriate OpenDoors
settings based on the following optional command-line parameters:

   -L or -LOCAL      - Causes door to operate in local mode, without
		       requiring a door information (drop) file.
   -B x or -BPS x    - Sets the bps (baud) rate to use.
   -P x or -PORT x   - Sets the serial port to use, were 0=COM1, 1=COM2,
		       etc.
   -N x or -NODE x   - Sets the node number to use.
   -?, -H or -HELP   - Displays command-line help and exits
   -PERSONALITY x    - Sets the sysop status line / function key
		       personality to use.
   -MAXTIME x	     - Sets the maximum number of minutes that any
		       user will be permitted to access the door.
   -ADDRESS x	     - Sets serial port address, to be used if FOSSIL
		       driver is not being used.
   -IRQ x	     - Sets the serial port IRQ line, to be used if
		       FOSSIL driver is not being used.
   -NOFOSSIL	     - Disables use of FOSSIL driver, even if it is
		       present.
   -NOFIFO	     - Disables use of 16550 FIFO buffers (only if
		       FOSSIL driver is not being used).
   -DROPFILE x	     - Door information file directory or
		       directory+filename.
   -USERNAME x	     - Name of user who is currently online.
   -TIMELEFT x	     - User's time remaining online.
   -SECURITY x	     - User's security level.
   -LOCATION x	     - Location from which user is calling.

Note that any information that is available from the door information
file overrides information provided on the command-line. If sufficient
parameters are provided on the command-line, the door can be operated
without a door information file. In order to do this, cmdline.c provides
a callback function that you can hook into od_control.od_no_file_func,
as demonstrated in tip4.c.

Case is not sensitive in the names of command line arguments.