Use background from environment

.vimrc

@@ -19,12 +19,20 @@ set sm
 set sw=4
 set tw=72
 set viminfo='100,<50,s10,h,%
+
 if has('reltime')
   set incsearch
 endif
 
+if $BG == "light"
+    set bg=light
     colorscheme hjp
     syntax on
+elseif $BG == "dark"
+    set bg=dark
+    syntax on
+endif
+
 map <F7> :cp
 map <F8> :cn
 map!  >I<yypa/O