title: grep and sed command
body: <p>i have a truckload of files with sql commands in them, i have been asked to extract all database table names from the files
  How can I use grep and sed to parse the files and create a list of the unique table names in a text file ..one per line?</p>
  
  <p>the name names all seem to start with "db_" which is handy!</p>
  
  <p>what would be the best way to use grep and sed together to pull the table names out?</p>