ch08_21.htm
来自「By Tom Christiansen and Nathan Torkingto」· HTM 代码 · 共 292 行
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<HTML><HEAD><TITLE>Recipe 8.20. Program: laston (Perl Cookbook)</TITLE><METANAME="DC.title"CONTENT="Perl Cookbook"><METANAME="DC.creator"CONTENT="Tom Christiansen & Nathan Torkington"><METANAME="DC.publisher"CONTENT="O'Reilly & Associates, Inc."><METANAME="DC.date"CONTENT="1999-07-02T01:38:58Z"><METANAME="DC.type"CONTENT="Text.Monograph"><METANAME="DC.format"CONTENT="text/html"SCHEME="MIME"><METANAME="DC.source"CONTENT="1-56592-243-3"SCHEME="ISBN"><METANAME="DC.language"CONTENT="en-US"><METANAME="generator"CONTENT="Jade 1.1/O'Reilly DocBook 3.0 to HTML 4.0"><LINKREV="made"HREF="mailto:online-books@oreilly.com"TITLE="Online Books Comments"><LINKREL="up"HREF="ch08_01.htm"TITLE="8. File Contents"><LINKREL="prev"HREF="ch08_20.htm"TITLE="8.19. Program: tctee"><LINKREL="next"HREF="ch09_01.htm"TITLE="9. Directories"></HEAD><BODYBGCOLOR="#FFFFFF"><img alt="Book Home" border="0" src="gifs/smbanner.gif" usemap="#banner-map" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Perl Cookbook"><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><p><TABLEWIDTH="684"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch08_20.htm"TITLE="8.19. Program: tctee"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 8.19. Program: tctee"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1"><ACLASS="chapter"REL="up"HREF="ch08_01.htm"TITLE="8. File Contents"></A></FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="chapter"HREF="ch09_01.htm"TITLE="9. Directories"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 9. Directories"BORDER="0"></A></TD></TR></TABLE></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="ch08-21741">8.20. Program: laston</A></H2><PCLASS="para"><ACLASS="indexterm"NAME="ch08-idx-1000004736-0"></A><ACLASS="indexterm"NAME="ch08-idx-1000004736-1"></A><ACLASS="indexterm"NAME="ch08-idx-1000004736-2"></A>When you log in to a Unix system, it tells you when you last logged in. That information is stored in a binary file called <EMCLASS="emphasis">lastlog</EM>. Each user has their own record; UID 8 is at record 8, UID 239 at record 239, and so on. To find out when a given user last logged in, convert their login name to a number, seek to their record in that file, read, and unpack. Doing so with shell tools is very hard, but it's very easy with the <EMCLASS="emphasis">laston</EM> program. Here's an example:</P><PRECLASS="programlisting">% laston gnat<CODECLASS="userinput"><B><CODECLASS="replaceable"><I>gnat UID 314 at Mon May 25 08:32:52 1998 on ttyp0 from below.perl.com</I></CODE></B></CODE></PRE><PCLASS="para">The program in <ACLASS="xref"HREF="ch08_21.htm#ch08-27836"TITLE="laston">Example 8.9</A> is much newer than the <CODECLASS="literal">tctee</CODE> program in <ACLASS="xref"HREF="ch08_20.htm#ch08-41455"TITLE="tctee">Example 8.8</A>, but it's less portable. It uses the Linux binary layout of the <EMCLASS="emphasis">lastlog</EM> file. You'll have to change this for other systems.</P><DIVCLASS="example"><H4CLASS="example"><ACLASS="title"NAME="ch08-27836">Example 8.9: laston</A></H4><PRECLASS="programlisting">#!/usr/bin/perl# laston - find out when given user last logged onuse User::pwent;use IO::Seekable qw(SEEK_SET);open (LASTLOG, "/var/log/lastlog") or die "can't open /usr/adm/lastlog: $!";$typedef = 'L A12 A16'; # linux fmt; sunos is "L A8 A16"$sizeof = length(pack($typedef, ()));for $user (@ARGV) { $U = ($user =~ /^\d+$/) ? getpwuid($user) : getpwnam($user); unless ($U) { warn "no such uid $user\n"; next; } seek(LASTLOG, $U->uid * $sizeof, SEEK_SET) or die "seek failed: $!"; read(LASTLOG, $buffer, $sizeof) == $sizeof or next; ($time, $line, $host) = unpack($typedef, $buffer); printf "%-8s UID %5d %s%s%s\n", $U->name, $U->uid, $time ? ("at " . localtime($time)) : "never logged in", $line && " on $line", $host && " from $host";<ACLASS="indexterm"NAME="ch08-idx-1000004738-0"></A><ACLASS="indexterm"NAME="ch08-idx-1000004738-1"></A><ACLASS="indexterm"NAME="ch08-idx-1000004738-2"></A>} <ACLASS="indexterm"NAME="ch08-idx-1000004576-0"></A></PRE></DIV></DIV><DIVCLASS="htmlnav"><P></P><HRALIGN="LEFT"WIDTH="684"TITLE="footer"><TABLEWIDTH="684"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch08_20.htm"TITLE="8.19. Program: tctee"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 8.19. Program: tctee"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><ACLASS="book"HREF="index.htm"TITLE="Perl Cookbook"><IMGSRC="../gifs/txthome.gif"ALT="Perl Cookbook"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="chapter"HREF="ch09_01.htm"TITLE="9. Directories"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 9. 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