find equal ref (from, to) in members of relation

relations

#!/bin/bash

#
# find equal ref (from, to) in members of relation
#
# @author  leite <[email protected]>
# @license GPL version 3
#

relation=0
id=0
from=0
to=0

while IFS='' read -r line || [[ -n "$line" ]]; do
  relation=$([[ $line == *"<relation "* ]] && echo 1 || echo $relation)
  if [[ $line == *"<relation "* ]]; then
    relation=1
    id=$(echo $line | sed -rn "s/.* id='([^']+)'.*/\1/ p")
  fi
  if [[ $relation -eq 1 ]]; then
    echo $line | grep " role='from'" >/dev/null && \
      from=$(echo $line | sed -rn "s/.* ref='([^']+)' role='from'.*/\1/ p")
    echo $line | grep " role='to'" >/dev/null && \
      to=$(echo $line | sed -rn "s/.* ref='([^']+)' role='to'.*/\1/ p")
  fi
  if [[ $line == *"</relation>"* ]]; then
    [[ $from -eq $to ]] && echo "relation ${id} duplicated!"
    relation=0
  fi
done < "$1"