how to use and sort uniq command to remove n characters from first and n characters after

Question

I am having file containing following lines

abcd15051969vignesh
efgh16071989ganesh
ijkl18091972murugesh
mnop15051969santhosh
qrst21061967mahesh
uvwx16071989suresh

now I want to sort the lines on the basis of date of birth and remove the duplicate lines containing same date of birth

Answer 1

You can tell sort to sort by date and to return unique values:

sort -u -k1.9,1.12 -k1.7,1.8 -k1.5,1.6 < input
      ^             ^
      |             |
    unique       start the sort
                 key at 1st word,
                 from char 7 to 8

Output

qrst21061967mahesh
abcd15051969vignesh
ijkl18091972murugesh
efgh16071989ganesh