Every word of a file can be placed on a separate line by typing
cat old_filename | tr -cs A-Za-z '\012' > new_filename
The following lists all words in filename in alphabetical order.
cat filename | tr -cs A-Za-z '\012' | tr A-Z a-z | sort | uniq
You can find out when the file .rhosts was last modified by
typing
echo .rhosts last modified on `/bin/ls -l .rhosts | cut -c33-44`
Typing head -n displays the first n lines of a file.
And typing last lists the last logins.