Re: [Qemu-devel] [PATCH] Allow default network type to be determined from an environmental variable

[M. Warner Losh]

In message: <address@hidden>
            Paul Brook <address@hidden> writes:
: > In the absence of a global configuration file, a reasonably sane way to
: > support this configuration system wide is to use an environmental
: > variable.  QEMU already uses a number of global variables for
: > configuring audio options.
: 
: I'd really prefer we didn't do this, and preferably obsoleted/removed the 
: existing environment variables.  IMHO using environment variables is a really 
: bad idea and should be avoided wherever possible.
: 
: Environment variables are about the worst user interface I can think of. For 
a 
: start they're a global resource, which is limited on some systems.
: It's also extremely hard to determine what environment a user is running. 
This 
: makes reproducing user bugs somewhere between hard and impossible.

Other than quick, developer friendly hacks, the only time environment
variables make sense is to select globally something.  A hypothetical
QEMU_ROOT might be useful for selecting which tree of files qemu reads
from.  If you had multiple shells and wanted to run different
installations of qmeu in each, this would be useful.  But to have them
control more fine grain options is something to be avoided.  At least
that's how I've selected them in my programs in the past....

Please note: I'm not saying this is the right way to select between
multiple installed versions of qemu, just an example of when it makes
sense.

Warner