V3/usr/man/man1/who.1

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NAME		who  --  who is on the system
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SYNOPSIS	who___ [ who-file ]
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DESCRIPTION	who___, without an argument,
lists the name, typewriter channel, and login time
for each current UNIX user.

Without an argument,
who___ examines the /tmp/utmp_________
file to obtain its information.
If a file is given, that file is examined.
Typically the given file will be /tmp/wtmp_________,
which contains a record of all the logins since it
was created.
Then who___ will list
logins, logouts, and crashes since the creation of
the wtmp file.

Each login is listed with user name, last character
of input device name (with /dev/tty________ suppressed),
date and time.
Certain logouts produce a similar line without a user name.
Reboots produce a line with "x" in the place of the device name,
and a fossil time indicative of when the system went down.
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FILES		/tmp/utmp
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SEE ALSO	login(I), init(VII)
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DIAGNOSTICS	"?" if a named file cannot be read.
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BUGS		--