By default, who gathers information from the file /var/run/utmpx; an alternative file may be specified

file

Write column headings above the regular output

Print system login processes (unsupported)

Only print information about the current terminal

Print active processes spawned by launchd(8) (unsupported)

'Quick mode': List only names and number of users currently logged on

List only the name, line and time fields (this is the default)

Print a character after the user name indicating the state of the terminal line: '+' writable, '-' not writable, '?' bad

Print last system clock change (unsupported)

Print the idle time for each user and the associated process ID

Name	Description
`-a`	Same as -bdlprTtu
`-b`	Time of last system boot
`-d`	Print dead processes
`-H`	Write column headings above the regular output
`-l`	Print system login processes (unsupported)
`-m`	Only print information about the current terminal
`-p`	Print active processes spawned by launchd(8) (unsupported)
`-q`	'Quick mode': List only names and number of users currently logged on
`-r`	Print the current runlevel
`-s`	List only the name, line and time fields (this is the default)
`-T`	Print a character after the user name indicating the state of the terminal line: '+' writable, '-' not writable, '?' bad
`-t`	Print last system clock change (unsupported)
`-u`	Print the idle time for each user and the associated process ID

who [file]