`who': Print who is currently logged in
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`who' prints information about users who are currently logged on.
Synopsis:
`who' [OPTION] [FILE] [am i]
If given no non-option arguments, `who' prints the following
information for each user currently logged on: login name, terminal
line, login time, and remote hostname or X display.
If given one non-option argument, `who' uses that instead of
`/var/run/utmp' as the name of the file containing the record of users
logged on. `/var/log/wtmp' is commonly given as an argument to `who'
to look at who has previously logged on.
If given two non-option arguments, `who' prints only the the entry
of the user invoking it. (Equivalent to `-m'.) Traditionally, the two
arguments given are `am i', as in `who am i'.
The program accepts the following options. Also see Note:Common
options.
`-a'
`--all'
Same as calling `who' with `-b -d --login -p -r -t -u'.
`-b'
`--boot'
Print the time of the last system boot.
`-d'
`--dead'
Print dead processes. Causes an additional field, EXIT, to be
printed. The EXIT field displays the termination and exit codes
for the process.
`-H'
`--heading'
Print a line of column headings.
`-i'
`--idle'
After the login time, print the number of hours and minutes that
the user has been idle. `.' means the user was active in last
minute. `old' means the user was idle for more than 24 hours.
NOTE: `-i' is deprecated, please use -u instead.
`--login'
Output login processes. This is equivalent to the SUS `-l' option,
which is currently used as the shortname for `--lookup'.
`-l'
`--lookup'
Attempt to canonicalize hostnames found in utmp through a DNS
lookup. This is not the default because it can cause significant
delays on systems with automatic dial-up internet access. NOTE:
this usage of `-l' is deprecated. (`-l' will mean `--login' in the
next release.)
`-m'
Output only items relating to the current terminal.
`-p'
`--process'
Output other active processes spawned by init.
`-q'
`--count'
Print only the login names and the number of users logged on.
Overrides all other options.
`-r'
`--runlevel'
Output the current runlevel.
`-s'
`--short'
Output only the NAME, LINE, and TIME fields. If no other options
are selected, this is the default.
`-t'
`--time'
Output the time of the last change to the system clock.
`--users'
`-u'
Output the users currently logged in. Adds the IDLE field, which
is the time since there was some activity on the user's terminal.
`-w'
`-T'
`--mesg'
`--message'
`--writable'
After each login name print a character indicating the user's
message status:
`+' allowing `write' messages
`-' disallowing `write' messages
`?' cannot find terminal device