who

早期freebsd实现

#!/usr/bin/perl
# This assumes your /etc/utmp file looks like ours
open(UTMP,'/etc/utmp');
@mo = (Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec);
while (read(UTMP,$utmp,36)) {
    ($line,$name,$host,$time) = unpack('A8A8A16l',$utmp);
    if ($name) {
	$host = "($host)" if ord($host);
	($sec,$min,$hour,$mday,$mon) = localtime($time);
	printf "%-9s%-8s%s %2d %02d:%02d   %s\n",
	  $name,$line,$mo[$mon],$mday,$hour,$min,$host;
    }
}