Editing Who (Unix) (section)

== Usage ==
The SUS without extensions only specifies the following <code>-m</code>, <code>-T</code>, and <code>-u</code> options, all other options are specified in the XSI extension.

:<code>-a</code>, process the system database used for user information with the <code>-b</code>, <code>-d</code>, <code>-l</code>, <code>-p</code>, <code>-r</code>, <code>-t</code>, <code>-T</code> and <code>-u</code>.
:<code>-b</code>, show time when system was last rebooted
:<code>-d</code>, show [[zombie process]]es and details
:<code>-H</code>, show column headers
:<code>-l</code>, show terminals where a user can log in
:<code>-m</code>, show information about the current terminal only
:<code>-p</code>, show active processes
:<code>-q</code>, quick format, show only names and the number of all users logged on, disables all other options; equivalent to '''users''' [[command line interface|command line]] utility
:<code>-r</code>, show runlevel of the [[init (Unix)|init]] process.
:<code>-s</code>, (default) show only name, terminal, and time details
:<code>-t</code>, show when system clock was last changed
:<code>-T</code>, show details of each terminal in a standard format (see note in Examples section)
:<code>-u</code>, show idle time; XSI shows users logged in and displays information whether the terminal has been used recently or not

Other Unix and [[Unix-like]] operating systems may add extra options. [[GNU]] {{mono|who}} includes a <code>-i</code> option behaving similarly to <code>-u</code> and a <code>-w</code> option displaying whether the user listed accepts messages (the SUS displays this when <code>-T</code> is specified), yet [[GNU]] <code>who</code> and [[BSD]] <code>who</code> both omit a number of the above options (such as <code>-a</code>, <code>-b</code>, <code>-d</code>, and others); [[GNU]] <code>who</code> instead uses <code>-l</code> to perform DNS lookups on hostnames listed.