look a |wc -l => 5985 look -b a |wc -l => 1228 look -bf a |wc -l => 1228 You must sort the /usr/share/dict/words file according to ignore case for the option

look a |wc -l => 5985 look -b a |wc -l => 1228 look -bf a |wc -l => 1228 You must sort the /usr/share/dict/words file according to ignore case for the option bf to work properly. Edit: I was expecting sort -f /usr/share/dict/words | look -bf a | wc -l to be 5985 but the result is 1228, don't know why.