Find missing tag

find_missing_tag.py

import sys

def main():
  last_line = ""
  for line in sys.stdin:
    if "<user>" in last_line and "<user>" in line:
      print "Here's the error, there is missing a close user tag before this point:"
      print line
      return
    last_line = line

if __name__ == '__main__':
  main()

grep

grep -Hin "</\?user>" Test.txt | python find_missing_tag.py 

Test.txt

<users>
  <user>
  </user>
  <user>
  <user>  
</users>