Thanks you all,
With your recomendations I built my solution as follows:
 :> writeLines(c("uno dos tres", "cuatro cinco", "seis"), "tempfile.txt")
 :> o <- pipe("wc < tempfile.txt", open="r")
 :> readLines(o)
 :[1] " 3  6 31"
best regards,
  --Sergio.