Removing commented lines and display

grep -v '^#' samba.conf 

here -v is for inverse 

ie -v, --invert-match
              Invert the sense of matching, to select non-matching lines.

Will print all lines EXCEPT those that begin with a # char. 

you can change the comment char to whatever you wish.

egrep -v '^(;|#|//)' filelist 

If you have more than one comment char , use the above command 

In regex, ^ indicates the beginning of a line, and $ the end of a line,

So ^$ specifies lines where the start of line character and the end of line character are right next to each other.