(sh-utils.info)who invocation

`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
`/etc/utmp' as the name of the file containing the record of users
logged on.  `/etc/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'.

   The program accepts the following options.  Also see Note: Common
options.

`-m'
     Same as `who am i'.

`-q'
`--count'
     Print only the login names and the number of users logged on.
     Overrides all other options.

`-s'
     Ignored; for compatibility with other versions of `who'.

`-i'
`-u'
`--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.

`-H'
`--heading'
     Print a line of column headings.

`-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