linux - Sed/Awk manipulation of a text -

i need change last column of file:

dir_/agra_2008_04_07_a  6   scd679  voice of male dir_/agra_2008_04_07_a  7   scd680  voice off dir_/agra_2007_10_01_a  2   scd502  voice on dir_/agra_2007_10_08_a  2   scd502  voice on 

to other:

dir_/agra_2008_04_07_a  6   scd679  voice_of_male dir_/agra_2008_04_07_a  7   scd680  voice_off dir_/agra_2007_10_01_a  2   scd502  voice_over dir_/agra_2007_10_08_a  2   scd502  voice_over 

adding underscores last column! anyone? thank you!

a simple sed solution:

sed 's/ /_/8g' file 

it replaces spaces underscores, ignoring first 7 occrences, hence starting 8th end (g). works if output has same number of spaces until last column.