1. To remove consecutive duplicate lines from a file:
uniq acc_nos accounts
This removes all consecutive duplicate lines from the file acc_nos and places the output in the file accounts.
2. To list the consecutive duplicate lines and the number of times that each occurs:
uniq -c tel_nos errors
This lists each of the consecutive duplicate lines in the file tel_nos and the number of times that each is repeated. The results are placed in the file errors.