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 `/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 2. 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.

`-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.

`-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