8.24. Program: tailwtmpEvery time a user logs into or out of a Unix system, a record is added to the wtmp file. You can't use the normal tail program on it, because the file is in binary format. The tailwtmp program in Example 8-7 knows the format of the binary file and shows every new record as it appears. You'll have to adjust the pack format for your own system. Example 8-7. tailwtmp#!/usr/bin/perl -w # tailwtmp - watch for logins and logouts; # uses linux utmp structure, from utmp(5) $typedef = "s x2 i A12 A4 l A8 A16 l"; $sizeof = length pack($typedef, ( ) ); use IO::File; open(WTMP, "< :raw", "/var/log/wtmp") or die "can't open /var/log/wtmp: $!"; seek(WTMP, 0, SEEK_END); for (;;) { while (read(WTMP, $buffer, $sizeof) = = $sizeof) { ($type, $pid, $line, $id, $time, $user, $host, $addr) = unpack($typedef, $buffer); next unless $user && ord($user) && $time; printf "%1d %-8s %-12s %2s %-24s %-16s %5d %08x\n", $type,$user,$line,$id,scalar(localtime($time)), $host,$pid,$addr; } for ($size = -s WTMP; $size = = -s WTMP; sleep 1) { } WTMP->clearerr( ); } Copyright © 2003 O'Reilly & Associates. All rights reserved. |
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