Hi Susan,

That was great !!

I am almost there - just one problem now.

Suppose my sample input.txt file now has just one line -

AAAAAGGGGGAAAAATTTTT

Now I want to use one of the command line utilities to PRINT on the screen the first matched group (or the first backreference.) I want to print the backreference ONLY.

I tried

a.

[shell]$ perl -pe '/.{5}(.{5})/' input.txt

it gave  AAAAAGGGGGAAAAATTTTT

b.

[shell]$ grep -oP ".{5}(.{5})" input.txt

AAAAAGGGGG
AAAAATTTTT

I just want to print the GGGGG on the screen from my input file.

Is there a quick way to do that using grep itself (I mean, of printing \1? ) or can I concatenate commands in "perl -pe"? or can I use any other single line command?

This is the last step :)

Thanks a lot for the help though!