;+
; NAME:
;   CMUNIQUE_ID
;
; AUTHOR:
;   Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770
;   craigm@lheamail.gsfc.nasa.gov
;
; PURPOSE:
;   Return a unique ID string
;
; CALLING SEQUENCE:
;   ID = CMUNIQUE_ID([STRINGVAL])
;
; DESCRIPTION: 
;
;   CMUNIQUE_ID returns a "unique" 8 character identifier.
;   Programmers can use this routine to derive unique strings which
;   can be used to write files, etc.
;
;   Identifiers are "unique" in the sense that it is unlikely that two
;   identifiers in a given IDL session will coincide.  Thus the
;   identifier is useful for constructing temporary filenames and
;   other hash values.  User routines are encouraged to append other
;   identifying information to this string, such as a session id, a
;   hostname, or a process id number.
;
;   The identifier is computed from various sources of random
;   information.  Users may supply additional information to be
;   scrambled into the identifier by passing the FODDER parameter.
;   CMUNIQUE_ID will return a different identifier upon each call,
;   with or without the FODDER keyword.  It maintains an internal
;   sequence counter, and and also scrambles in the system time.
;   These practices should ensure that successive identifiers are
;   different from one another.
;
; INPUTS:
;
;   FODDER - Any scalar string value.  These values are used to
;            additionally scramble the identifier.
;
; KEYWORDS:
;
;   NONE
;
; RETURNS:
;   The 8-character identifier string.
;
; EXAMPLE:
;   
;   Print two distinct identifiers.
;     IDL> print, cmunique_id(), ' ', cmunique_id()
;     29C47600 79061C57
;
; SEE ALSO:
;
;   NONE
;
; MODIFICATION HISTORY:
;   Written, CM, 11 Jan 2001
;
; $Id: cmunique_id.pro,v 1.2 2001/01/13 04:08:30 craigm Exp $
;
;-
; Copyright (C) 2001, Craig Markwardt
; This software is provided as is without any warranty whatsoever.
; Permission to use, copy, modify, and distribute modified or
; unmodified copies is granted, provided this copyright and disclaimer
; are included unchanged.
;-