#! /usr/bin/gawk -f

# Enumerates all trigraphs in the input file.
# Lines are implicitly padded with 2 blanks on either side.

/./ {
   m = length($0)
   str = ("  " $0 "  ")
   for( i=1; i<= m+2; i++ )
     { print substr(str, i, 3) }
   next
 }

/^$/ { next }