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<title>Postfix PCRE Support</title>
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<h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix PCRE Support</h1>
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<h2>PCRE (Perl Compatible Regular Expressions) map support</h2>
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<p> The optional "pcre" map type allows you to specify regular
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expressions with the PERL style notation such as \s for space and
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\S for non-space. The main benefit, however, is that pcre lookups
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are often faster than regexp lookups. This is because the pcre
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implementation is often more efficient than the POSIX regular
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expression implementation that you find on many systems. </p>
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<p> A description of how to use pcre tables, including examples,
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is given in the <a href="pcre_table.5.html">pcre_table(5)</a> manual page. Information about PCRE
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itself can be found at <a href="http://www.pcre.org/">http://www.pcre.org/</a>. </p>
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<h2>Building Postfix with PCRE support</h2>
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<p> Note: to use pcre with Debian GNU/Linux's Postfix, all you
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need is to install the postfix-pcre package and you're done. There
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is no need to recompile Postfix. </p>
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<p> In some future, Postfix will have a plug-in interface for adding
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map types. Until then, you need to compile PCRE support into Postfix.
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<p> First of all, you need the PCRE library (Perl Compatible Regular
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Expressions), which can be obtained from: </p>
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<a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/">ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/</a>.
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<p> NOTE: pcre versions prior to 2.06 cannot be used. </p>
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<p> In order to build Postfix with PCRE support you need to add
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-DHAS_PCRE and a -I for the PCRE include file to CCARGS, and add
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the path to the PCRE library to AUXLIBS, for example: </p>
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make -f Makefile.init makefiles \
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"CCARGS=-DHAS_PCRE -I/usr/local/include" \
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"AUXLIBS=-L/usr/local/lib -lpcre"
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<h2>Things to know</h2>
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<li> <p> When Postfix searches a <a href="pcre_table.5.html">pcre</a>: or <a href="regexp_table.5.html">regexp</a>: lookup table,
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each pattern is applied to the entire input string. Depending on
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the application, that string is an entire client hostname, an entire
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client IP address, or an entire mail address. Thus, no parent domain
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or parent network search is done, "user@domain" mail addresses are
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not broken up into their user and domain constituent parts, and
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"user+foo" is not broken up into user and foo. </p>
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<li> <p> Regular expression tables such as <a href="pcre_table.5.html">pcre</a>: or <a href="regexp_table.5.html">regexp</a>: are
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not allowed to do $number substitution in lookup results that can
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be security sensitive: currently, that restriction applies to the
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local <a href="aliases.5.html">aliases(5)</a> database or the <a href="virtual.8.html">virtual(8)</a> delivery agent tables.