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<HTML><HEAD><TITLE>Recipe 20.10. Mirroring Web Pages (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="1999-07-02T01:46:01Z"><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="ch20_01.htm"TITLE="20. Web Automation"><LINKREL="prev"HREF="ch20_10.htm"TITLE="20.9. Creating HTML Templates"><LINKREL="next"HREF="ch20_12.htm"TITLE="20.11. Creating a Robot"></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="ch20_10.htm"TITLE="20.9. Creating HTML Templates"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 20.9. Creating HTML Templates"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1"><ACLASS="chapter"REL="up"HREF="ch20_01.htm"TITLE="20. Web Automation"></A></FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch20_12.htm"TITLE="20.11. Creating a Robot"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 20.11. Creating a Robot"BORDER="0"></A></TD></TR></TABLE></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="ch20-21335">20.10. Mirroring Web Pages</A></H2><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch20-pgfId-1205">Problem<ACLASS="indexterm"NAME="ch20-idx-1000002666-0"></A><ACLASS="indexterm"NAME="ch20-idx-1000002666-1"></A><ACLASS="indexterm"NAME="ch20-idx-1000002666-2"></A><ACLASS="indexterm"NAME="ch20-idx-1000002666-3"></A></A></H3><PCLASS="para">You want to keep a local copy of a web page up-to-date.</P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch20-pgfId-1211">Solution</A></H3><PCLASS="para">Use LWP::Simple's <CODECLASS="literal">mirror</CODE> function:</P><PRECLASS="programlisting">use LWP::Simple;mirror($URL, $local_filename);</PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch20-pgfId-1221">Discussion</A></H3><PCLASS="para">Although closely related to the <CODECLASS="literal">get</CODE> function discussed in <ACLASS="xref"HREF="ch20_02.htm"TITLE="Fetching a URL from a Perl Script">Recipe 20.1</A>, the <CODECLASS="literal">mirror</CODE> function doesn't download the file unconditionally. It adds the <CODECLASS="literal">If-Modified-Since</CODE><ACLASS="indexterm"NAME="ch20-idx-1000003787-0"></A> header to the GET request it creates, so the server will not transfer the file unless it has been updated.</P><PCLASS="para">The <CODECLASS="literal">mirror</CODE> function mirrors only a single page, not a full tree. To mirror a set of pages, use this recipe in conjunction <ACLASS="xref"HREF="ch20_04.htm"TITLE="Extracting URLs">Recipe 20.3</A>. A good solution to mirroring an entire remote tree can be found in the w3mir program, also found on CPAN.</P><PCLASS="para">Be careful! It's possible (and easy) to write programs that run amok and begin downloading all web pages on the net. This is not only poor etiquette, it's also an infinite task, since some pages are dynamically generated. It could also get you into trouble with someone who doesn't want their pages downloaded en masse.</P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch20-pgfId-1231">See Also</A></H3><PCLASS="para">The documentation for the CPAN module LWP::Simple; the HTTP specification at <ACLASS="systemitem.url"HREF="http://www.w3.org/pub/WWW/Protocols/HTTP/">http://www.w3.org/pub/WWW/Protocols/HTTP/</A></P></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="ch20_10.htm"TITLE="20.9. Creating HTML Templates"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 20.9. 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