Bash – Clarification for Bash documentation on disown builtin option -h

bash, zsh and ksh93 are the shells that have a disown command. Of the three, bash is the only one that supports a h option. Without -h it emultates zsh behavior (remove from the job table), while with -h it emulates ksh93 behavior (will not send it a SIGHUP upon exit, but doesn't remove it from the job table so you can still bg or fg or kill it).

You could emulate that behavior with zsh, by doing:

typeset -A nohup
trap 'disown %${(k)^nohup}' EXIT
trap 'for i (${(k)nohup}) (($+jobstate[i])) || unset "nohup[$i]"' CHLD

So the nohup associative array holds the list of jobs that are not to be sent a SIGHUP upon exit. So, instead of disown -h %1, you'd write nohup[1]=.

See also setopt nohup to not send SIGHUP to any job upon exit.

Bash seems to send the SIGHUP only if it self received a SIGHUP, which for example occurs when a virtual terminal is closed or when the SSH connection is interrupted. From the documentation:

The shell exits by default upon receipt of a SIGHUP. Before exiting, an interactive shell resends the SIGHUP to all jobs, running or stopped. Stopped jobs are sent SIGCONT to ensure that they receive the SIGHUP. To prevent the shell from sending the SIGHUP signal to a particular job, it should be removed from the jobs table with the disown builtin (see Job Control Builtins) or marked to not receive SIGHUP using disown -h.

So if you type exit or press Ctrl+D all background process will remain, since this does not send a hang up signal to the Bash.

You can force Bash to warn you about the fact that there are still running background processes with

shopt -s checkjobs

There is an option to send the SIGHUP on exit if you are in an interactive shell(see here). But it doesn't work on my machine with Bash 4.2.25. Maybe it works for you

shopt -s huponexit