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From: achrist@easystreet.com
Newsgroups: comp.lang.ada
Subject: Re: How to find directory where the program is?
Date: Fri, 26 Apr 2002 13:41:36 -0700
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Date: 2002-04-26T13:41:36-07:00
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Stephen Leake wrote:
> 
> Most OS's have "environment variables". The hard part is getting the
> installer to set the appropriate environment variable.
> 

Problem if the installer runs on machine A and then user tries to
execute the program from machine 2. Much worse is the possibility 
that sometime during the lifetime of the installed program, the 
computer will be messed with by someone who removes the environment 
variable to clean up the environment or tidy up the startup script 
that sets the variables.  The environment is not a database; if a 
computer has lots of software installed and lots of environment 
settings, this is both an efficiency issue and a management problem.  

A user-friendly program will not simply crash if the required 
environment is missing.  My preferred approach is like the method 
of Hansel and Gretel in the deep woods -- drop lots of breadcrumbs.  
If you can't find your way based on the command line, look in the 
current  directory; if the current directory is no help, look in the 
environment (or the registry); if the environment doesn't help, look 
along the PATH;  if the path is no help, look in the program's 
directory.   

This gives some opportunity for confusion, but it also allows a 
hierarchical set of defaults and overrides of various options.  In
particular, it also llows running/testing of multiple versions of 
the same  program on the same machine with different settings that 
maybe don't interfere with each other.


Al