Novice from Competent:
Which command will find all the lines in a file containing the word "cheese"?
Competent from Expert:
Which command will extract all and only the words containing the letters "db" from a file?
cat file | grep -w db | sort -u |
grep db file | tr " " "n" | sort -u |
tac file | grep -i db | sort | uniq |
grep -o -E 'w+' file | uniq |