#! /usr/bin/gawk -f 

# Renumbers all units sequentially from 0001 in the INDEX index
# Usage: renumber-units < INDEX.old > INDEX.new

BEGIN {FS = ":"; OFS=":"; n = 0;}

/^[#]/ { print; next; }

(NF>0) {
  if (NF != 8) { printf "line %d, bad format\n", FNR > "/dev/stderr"; exit 1; }
  n++; $1=sprintf("%04d", n);
  print;
}