#! /usr/bin/gawk -f

# Enumerates all digraphs in the input file.
# Lines are implicitly padded with a blank on either side.

/./ {
   m = length($0)
   str = (" " $0 " ")
   for( i=1; i<= m+1; i++ )
     { print substr(str, i, 2) }
   next
 }

/^$/ { next }