coreutils: who invocation

1 
1 20.6 ‘who’: Print who is currently logged in
1 ============================================
1 
1 ‘who’ prints information about users who are currently logged on.
1 Synopsis:
1 
1      who [OPTION] [FILE] [am i]
1 
1    If given no non-option arguments, ‘who’ prints the following
1 information for each user currently logged on: login name, terminal
1 line, login time, and remote hostname or X display.
1 
1    If given one non-option argument, ‘who’ uses that instead of a
1 default system-maintained file (often ‘/var/run/utmp’ or ‘/etc/utmp’) as
1 the name of the file containing the record of users logged on.
1 ‘/var/log/wtmp’ is commonly given as an argument to ‘who’ to look at who
1 has previously logged on.
1 
1    If given two non-option arguments, ‘who’ prints only the entry for
1 the user running it (determined from its standard input), preceded by
1 the hostname.  Traditionally, the two arguments given are ‘am i’, as in
1 ‘who am i’.
1 
1    Timestamps are listed according to the time zone rules specified by
1 the ‘TZ’ environment variable, or by the system default rules if ‘TZ’ is
1 not set.  ⇒Specifying the Time Zone with ‘TZ’ (libc)TZ Variable.
1 
11    The program accepts the following options.  Also see ⇒Common
 options.
1 
1 ‘-a’
1 ‘--all’
1      Same as ‘-b -d --login -p -r -t -T -u’.
1 
1 ‘-b’
1 ‘--boot’
1      Print the date and time of last system boot.
1 
1 ‘-d’
1 ‘--dead’
1      Print information corresponding to dead processes.
1 
1 ‘-H’
1 ‘--heading’
1      Print a line of column headings.
1 
1 ‘-l’
1 ‘--login’
1      List only the entries that correspond to processes via which the
1      system is waiting for a user to login.  The user name is always
1      ‘LOGIN’.
1 
1 ‘--lookup’
1      Attempt to canonicalize hostnames found in utmp through a DNS
1      lookup.  This is not the default because it can cause significant
1      delays on systems with automatic dial-up internet access.
1 
1 ‘-m’
1      Same as ‘who am i’.
1 
1 ‘-p’
1 ‘--process’
1      List active processes spawned by init.
1 
1 ‘-q’
1 ‘--count’
1      Print only the login names and the number of users logged on.
1      Overrides all other options.
1 
1 ‘-r’
1 ‘--runlevel’
1      Print the current (and maybe previous) run-level of the init
1      process.
1 
1 ‘-s’
1      Ignored; for compatibility with other versions of ‘who’.
1 
1 ‘-t’
1 ‘--time’
1      Print last system clock change.
1 
1 ‘-u’
1      After the login time, print the number of hours and minutes that
1      the user has been idle.  ‘.’ means the user was active in the last
1      minute.  ‘old’ means the user has been idle for more than 24 hours.
1 
1 ‘-w’
1 ‘-T’
1 ‘--mesg’
1 ‘--message’
1 ‘--writable’
1      After each login name print a character indicating the user’s
1      message status:
1 
1           ‘+’ allowing ‘write’ messages
1           ‘-’ disallowing ‘write’ messages
1           ‘?’ cannot find terminal device
1 
1    The ‘who’ command is installed only on platforms with the POSIX
1 ‘<utmpx.h>’ include file or equivalent, so portable scripts should not
1 rely on its existence on non-POSIX platforms.
1 
1    An exit status of zero indicates success, and a nonzero value
1 indicates failure.
1