Unix in a Nutshell, 4th Edition

Name

who

Synopsis

    who [options] [file]

Display information about the current status of the system. With no options, list the names of users currently logged in to the system. An optional system file (the default varies per system) can be supplied to give additional information. who is usually invoked without options, but useful options include am i and -u. For more examples, see cut, line, paste, tee, and wc.

Common Options

-H, --heading

Print headings.

-m

Report only about the current terminal.

-q, --count

“Quick.” Display only the usernames.

-s, --short

List the name, line, and time fields (the default behavior).

-T, --mesg, --message, --writable

Report whether terminals are writable (+), not writable (-), or unknown (?).

-u, --users

Report terminal usage (idle time). A dot (.) means less than one minute idle; old means more than 24 hours idle.

am i

Print the username of the invoking user. (Similar to results from id.)

Solaris and GNU/Linux Options

-a, --all

Use the -b, -d, -l, -p, -r, -t, -T, and -u options.

-b, --boot

Report information about the last reboot.

-d, --dead

Report expired processes.

-l, --login

Report inactive terminal lines.

-p, --process

Report previously spawned processes.

-r, --runlevel

Report the run level.

-t, --time

Report the last change of the system clock (via date).

Solaris Option

-n x

Display x users per line (works only with -q).

GNU/Linux Options

-i, --idle

Present idle time as HOURS:MINUTES, . (dot), or old. (Deprecated; use -u.)

--lookup

Use DNS to canonicalize hostnames for people ...