The ask here is, when a logged-in user logs out of the ssh session, the system must execute a specific script or a command. So it is like configuring a post script or a trigger to perform the desired action when the user is logged out of the ssh session.

This can be easily done with the help of pam module in CentOS/RHEL systems. Follow the steps outlined below to configure the pam module.

1. Add the below entry to the pam configuration file /etc/pam.d/sshd:

# vi /etc/pam.d/sshd
session     optional    pam_exec.so quiet /var/tmp/post_session.sh

Here,
/var/tmp/post_session.sh is our script which will run when the user is logged out.

The /etc/pam.d/sshd configuration file should look like below:

# cat /etc/pam.d/sshd 
#%PAM-1.0
auth    required pam_sepermit.so
auth       substack     password-auth
auth       include      postlogin
# Used with polkit to reauthorize users in remote sessions
-auth      optional     pam_reauthorize.so prepare
account    required     pam_nologin.so
account    required     pam_access.so
account    include      password-auth
password   include      password-auth
# pam_selinux.so close should be the first session rule
session    required     pam_selinux.so close
session    required     pam_loginuid.so
# pam_selinux.so open should only be followed by sessions to be executed 
in the user context
session    required     pam_selinux.so open env_params
session    required     pam_namespace.so
####Trigger with user logout #####
session     optional    pam_exec.so quiet /var/tmp/post_session.sh
####
session    optional     pam_keyinit.so force revoke
session    include      password-auth
session    include      postlogin
# Used with polkit to reauthorize users in remote sessions
-session   optional     pam_reauthorize.so prepare

2. Now you can configure the post trigger script as per you requirement. For the sake of this post I will just append the time of user logout into a file. For example:

# cat /var/tmp/post_session.sh
#!/bin/bash
if [ "$PAM_TYPE" = "close_session" ]; then
date >> /var/tmp/user_logout.out        ##  This is the action to be performed when user logs out.
fi

3. Grant the execute permission to the /var/tmp/post_session.sh script.

# chmod ugo+x /var/tmp/post_session.sh

4. Verify by logging in and out multiple time and you should get the time of all the logouts added to the file /var/tmp/user_logout.out.