Bash – Unix will background running process stopped after disconnect the session

cat /proc/<pid>/environ

If you want to have pid(s) of a given running executable you can, among a number of other possibilities, use pidof:

AlberT$ pidof sshd   
30690 6512 

EDIT:

I totally quote Dennis Williamson and Teddy comments to achieve a more readable output. My solution is the following:

tr '\0' '\n' < /proc/<pid>/environ

Answer found.

For BASH, this depends on the huponexit shell option, which can be viewed and/or set using the built-in shopt command.

Looks like this options is off by default, at least on RedHat-based systems.

More info on the BASH man page:

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 signal to a particular job, it should be removed from the jobs table with the disown builtin (see SHELL BUILTIN COMMANDS below) or marked to not receive SIGHUP using disown -h.

If the huponexit shell option has been set with shopt, bash sends a SIGHUP to all jobs when an interactive login shell exits.