cut -d " " -f1 | head -n 1                  #Output first column and first line
cut -d ":" -f 1,3 /etc/passwd               #Output 1th and 3rd line
cut -d " " -f1 | sed sed -n "$i"p file      #search line "i" in file
cut -d " " -f1 | sed -n "1"p file           #search line "1" in file