#!/usr/bin/perl

sub read_utmp {
	# type pid line id user host termination exit session sec usec addr pad
	my $UTMP_TEMPLATE = "i i A32 A4 A32 A256 s s I I I I4 A20";
	# size of "struct utmp"
	my $UTMP_LENGTH = 384;
	my ($fname) = shift;
	my $buf, @data;

	if(!open(UTMP, $fname)) {
		print STDERR "$fname: cannot open.\n";
		return 0;
	}
	while(read(UTMP, $buf, $UTMP_LENGTH) == $UTMP_LENGTH) {
		@data = unpack($UTMP_TEMPLATE, $buf);
		printf("type=%d pid=%d line=%s id=%s user=%s\n",
			$data[0], $data[1], $data[2], $data[3], $data[4]);
		printf("\thost=%s exit=%d/%d session=%d\n",
			$data[5], $data[6], $data[7], $data[8]);
		printf("\ttime=%d.%06d (" . localtime($data[9]) . ")\n",
			$data[9], $data[10]);
	}
	close UTMP;
}

### MAIN

my $fname = "/var/log/wtmp";

if($ARGV[0]) {
	while($fname = shift) {
		&read_utmp($fname);
	}
} else {
	&read_utmp($fname);
}