The following commands are helpful for seeing if a user is currently logged in, or when the last time a user was on.
Who
The “who” command give information about users that are currently logged in
[steve@localhost ~]$ who
root pts/0 2018-12-14 15:05 (192.168.1.23)
steve pts/2 2018-12-14 12:09 (192.168.1.25)
[steve@localhost ~]$
Last
The last command shows a list of the last logged in users
[steve@localhost ~]$ last
steve pts/2 192.168.1.25 Fri Dec 14 15:05 still logged in
root pts/1 192.168.1.23 Fri Dec 14 12:09 - 12:09 (00:00)
steve tty1 Thu Nov 8 10:02 - 10:15 (00:13)
reboot system boot 4.7.0.x Thu Nov 8 09:01 - 10:12 (01:01)
wtmp begins Tue Oct 11 09:01:57 2018
[steve@localhost ~]$