.SH ENVIRONMENT
This section describes environment variables that control Chocolate Doom's
behavior.
.TP 
\fBDOOMWADDIR\fR, \fBDOOMWADPATH\fR
These environment variables provide paths to search for Doom .WAD files when
looking for a game IWAD file or a PWAD file specified with the '-file' option.
\fBDOOMWADDIR\fR specifies a single path in which to look for WAD files,
while \fBDOOMWWADDIR\fR specifies a colon-separated list of paths to search.
.TP
\fBPCSOUND_DRIVER\fR
When running in PC speaker sound effect mode, this environment variable 
specifies a PC speaker driver to use for sound effect playback.  Valid
options are "Linux" for the Linux console mode driver, "BSD" for the
NetBSD/OpenBSD PC speaker driver, and "SDL" for SDL-based emulated PC speaker 
playback (using the digital output).