The
who
utility displays a list of all users currently logged on, showing for
each user the login name, tty name, the date and time of login, and
hostname if not local.
The options are as follows:
-H
Write column headings above the regular output.
-m
Only print information about the current terminal.
This is the
POSIX
way of saying
whoami.
-q
(Quick.)
List only the names and the number of users currently logged on.
When this option is used, all other options are ignored.
-T
Print a character after the user name indicating the state of the
terminal line:
‘+’
if the terminal is writable;
‘\-’
if it is not;
and
‘\&?’
if a bad line is encountered.
-u
Print the idle time for each user.
\&amI
Returns the invoker's real user name.
file
By default,
who
gathers information from the file
/var/run/utmp.
An alternate
file
may be specified which is usually
/var/log/wtmp
(or
/var/log/wtmp.[0-6]
depending on site policy as
wtmp
can grow quite large and daily versions may or may not
be kept around after compression by
ac(8/)).
The
wtmp
file contains a record of every login, logout,
crash, shutdown and date change
since
wtmp
was last truncated or
created.
If
/var/log/wtmp
is being used as the file, the user name may be empty
or one of the special characters
"|",
"}",
and
"\&~".
Logouts produce an output line without any user name.
For more information on the special characters, see
utmp(5).