tr ' ' '\012' < btl.txt | grep '_N' | wc 273117 273117 2938027 [273,117/1,014,312=.269 Nouns account for 26.8%] tr ' ' '\012' < btl.txt | egrep '_V|_B|_DO|_H|_M' | wc 182903 182903 1815809 [182,903/1,014,312=.180 Verbs account for 18.0%]
The shortcut for nouns is possible because all noun tags in the Brown tagset start with N, and no other tags do. Foreign nouns were not counted in the results given in the textbook.