grass-R (?)

i'm trying to use some tutorial for grass-R

i've installed all the spatial packages, but after the command :

G <- gmeta6()

i've his error :

 > library(spgrass6)
 > G <- gmeta6()
sh: line 1: g.region: command not found
Errore in if (is.na(projstr)) uprojargs <- projstr else uprojargs <-  
paste(unique(unlist(strsplit(projstr,  :
	l'argomento ha lunghezza zero
sh: line 1: g.proj: command not found
 >


can you help me?
Massimo.