Gnu/coreutils/who-invocation
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20.6 who
: Print who is currently logged in
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
a default system-maintained file (often /var/run/utmp
or
/etc/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 entry
for the user running it (determined from its standard input), preceded
by the hostname. Traditionally, the two arguments given are ‘am i
’, as in ‘who am i
’.
Timestamps are listed according to the time zone rules specified by
the TZ
environment variable, or by the system default rules if
TZ
is not set. See [https://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html#TZ-Variable Specifying the Time Zone
with TZ
] in The GNU C Library Reference Manual.
The program accepts the following options. Also see Common options.
- ‘
-a
’
‘--all
’ Same as ‘
-b -d --login -p -r -t -T -u
’.- ‘
-b
’
‘--boot
’ Print the date and time of last system boot.
- ‘
-d
’
‘--dead
’ Print information corresponding to dead processes.
- ‘
-H
’
‘--heading
’ Print a line of column headings.
- ‘
-l
’
‘--login
’ List only the entries that correspond to processes via which the system is waiting for a user to login. The user name is always ‘
LOGIN
’.- ‘
--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.
- ‘
-m
’ Same as ‘
who am i
’.- ‘
-p
’
‘--process
’ List 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
’ Print the current (and maybe previous) run-level of the init process.
- ‘
-s
’ Ignored; for compatibility with other versions of
who
.- ‘
-t
’
‘--time
’ Print last system clock change.
- ‘
-u
’ After the login time, print the number of hours and minutes that the user has been idle. ‘
.
’ means the user was active in the last minute. ‘old
’ means the user has been idle for more than 24 hours.- ‘
-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
The who
command is installed only on platforms with the
POSIX <utmpx.h>
include file or equivalent, so portable scripts
should not rely on its existence on non-POSIX platforms.
An exit status of zero indicates success, and a nonzero value indicates failure.
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