The who command is valuable for determining who is currently logged in to a system. In this project, you try out the who command using several options.

To use the who command to determine who is logged in to the system:

$1.$ Type who in the command line, and press Enter.

$2.$ You see a list showing user names, the terminals $($lines$)$ they are using, and the dates and the times they logged in$.$ For example, for your connection you will likely see the lines pts$/1,$ :$0,$ or both, which show you are logged on locally. Users who are logged on remotely will have lines that begin with tty$,$ such as tty$1,$ tty$2,$ and so on$.$

$3.$ To display a line of column headings with the who command$$s output, type who $-$H and press Enter.

If any current users are logged in from a remote host, the COMMENT column shows the name of the host$\mathrm{.}4.$ Idle time is the amount of time that has elapsed with no activity in a user$$s session. Type who $-$u and press Enter to see each user$$s idle time. The following is a sample listing of who information. $($The final value is the process ID$,$ but you might also see a

comment after the process ID$.)$

mpalmer pts$/12009-11-2208$:$154230($:$0\mathrm{.}0)$

sjones tty$12009-11-2207$:$564229($:$29\mathrm{.}0)$

rsanchez tty$32009-11-2208$:$214238$ old

The output shows that the person logged in as mpalmer has been active in the last minute. The account sjones has no activity in the last $29$ minutes. The word $$old$$ on rsanchez$$s line indicates no activity in the past $24$ hours.

$5.$ If you want to use multiple options on the same command line, type them all after a single hyphen. For example, type who $-$uH and press Enter to see a list of users with idle times and column headings.

$6.$ Type who $-$q and press Enter to see a quick list of current users. You see a list simi$-$ lar to the following, which shows only login names and the total number of users on the system.

mpalmer sjones rsanchez

# users$=3$

$7.$ To determine which terminal you are using or what time you logged in$,$ type who am i in the command line, and press Enter $($see Figure $1-15).$ What information appears? If you are not certain, type who am i $-$H and press Enter to view column headings. $($Another option is to type whoami as one word, which only displays your account name or user ID$,$ in case you are not certain which account you are cur$-$ rently using; this option is often used by system administrators. Also try entering who mom likes to see what you find out.$)$