How bash handles the jobs when logout?

Question

As far as I understood from the books and bash manuals is that. When a user logs out from bash all the background jobs that is started by the user will automatically termina

Answer 1

Whether running background jobs are terminated on exit depends on the shell. Bash normally does not do this, but can be configured to for login shells (shopt -s huponexit). In any case, access to the tty is impossible after the controlling process (such as a login shell) has terminated.

Situations that do always cause SIGHUP include:

• Anything in foreground when the tty is closed down.
• Any background job that includes stopped processes when their shell terminates (SIGCONT and SIGHUP). Shells typically warn you before letting this happen.

huponexit summary:

• On: Background jobs will be terminated with SIGHUP when shell exits

  $ shopt -s huponexit
  $ shopt huponexit
  huponexit       on
  

• Off: Background jobs will NOT be terminated with SIGHUP when shell exits.

  $ shopt -u huponexit
  $ shopt huponexit
  huponexit       off
  

Answer 2

Only interactive shells kill jobs when you close them. Other shells (for example those you get by using su - username) don't do that. And interactive shells only kill direct subprocesses.