The following entries are displayed for each user: login name, the tty name, the remote host, login time, idle time, JCPU, PCPU, and the command line of their current process.
The JCPU time is the time used by all processes attached to the tty. It does not include past background jobs, but does include currently running background jobs.
The PCPU time is the time used by the current process, named in the "what"
/etc/utmp information about who is currently logged on /proc process information