title: What content do -shm and -wal files contain after running checkpoint?
body: <p>I am taking the backup of SQLite DB using cp command after running wal_checkpoint(FULL). The DB is being used in WAL mode so there are other files like -shm and -wal in my folder.
  When I run wal_checkpoint(FULL), the changes in WAL file get committed to the database. I was wondering whether -wal and -shm files get deleted after running a checkpoint. If not, then what do they contain ?</p>
  <p>I know my backup process is not good since I am not using SQLite backup APIs. This is a bug in my code.</p>