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      8 <title>Postfix PCRE Support</title>
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     17 <h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix PCRE Support</h1>
     18 
     19 <hr>
     20 
     21 <h2>PCRE (Perl Compatible Regular Expressions) map support</h2>
     22 
     23 <p> The optional "pcre" map type allows you to specify regular
     24 expressions with the PERL style notation such as \s for space and
     25 \S for non-space. The main benefit, however, is that pcre lookups
     26 are often faster than regexp lookups. This is because the pcre
     27 implementation is often more efficient than the POSIX regular
     28 expression implementation that you find on many systems. </p>
     29 
     30 <p> A description of how to use pcre tables, including examples,
     31 is given in the <a href="pcre_table.5.html">pcre_table(5)</a> manual page. Information about PCRE
     32 itself can be found at <a href="https://www.pcre.org/">https://www.pcre.org/</a>. </p>
     33 
     34 <h2>Using Postfix packages with PCRE support</h2>
     35 
     36 <p> To use pcre with Debian GNU/Linux's Postfix, or with Fedora or
     37 RHEL Postfix, all you
     38 need is to install the postfix-pcre package and you're done.  There
     39 is no need to recompile Postfix. </p>
     40 
     41 <h2>Building Postfix from source with PCRE support</h2>
     42 
     43 <p> These instructions assume that you build Postfix from source
     44 code as described in the <a href="INSTALL.html">INSTALL</a> document. </p>
     45 
     46 <p> To build Postfix from source with pcre support, you need a pcre
     47 library. Install a vendor package, or download the source code from
     48 locations in <a href="https://www.pcre.org/">https://www.pcre.org/</a> and build that yourself.
     49 
     50 <p> Postfix can build with the pcre2 library or the legacy pcre
     51 library. It's probably easiest to let the Postfix build procedure
     52 pick one. The following commands will first discover if the pcre2
     53 library is installed, and if that is not available, will discover
     54 if the legacy pcre library is installed. </p>
     55 
     56 <blockquote>
     57 <pre>
     58 $ make -f Makefile.init makefiles 
     59 $ make
     60 </pre>
     61 </blockquote>
     62 
     63 <p> To build Postfix explicitly with a pcre2 library (Postfix 3.7
     64 and later): </p>
     65 
     66 <blockquote>
     67 <pre>
     68 $ make -f Makefile.init makefiles \
     69     "CCARGS=-DHAS_PCRE=2 `pcre2-config --cflags`" \
     70     "<a href="PCRE_README.html">AUXLIBS_PCRE</a>=`pcre2-config --libs8`"
     71 $ make
     72 </pre>
     73 </blockquote>
     74 
     75 <p> To build Postfix explicitly with a legacy pcre library (all
     76 Postfix versions): </p>
     77 
     78 <blockquote>
     79 <pre>
     80 $ make -f Makefile.init makefiles \
     81     "CCARGS=-DHAS_PCRE=1 `pcre-config --cflags`" \
     82     "<a href="PCRE_README.html">AUXLIBS_PCRE</a>=`pcre-config --libs`"
     83 $ make
     84 </pre>
     85 </blockquote>
     86 
     87 <p> Postfix versions before 3.0 use AUXLIBS instead of <a href="PCRE_README.html">AUXLIBS_PCRE</a>.
     88 With Postfix 3.0 and later, the old AUXLIBS variable still supports
     89 building a statically-loaded PCRE database client, but only the new
     90 <a href="PCRE_README.html">AUXLIBS_PCRE</a> variable supports building a dynamically-loaded or 
     91 statically-loaded PCRE database client.  </p>
     92 
     93 <blockquote>
     94  
     95 <p> Failure to use the <a href="PCRE_README.html">AUXLIBS_PCRE</a> variable will defeat the purpose
     96 of dynamic database client loading. Every Postfix executable file
     97 will have PCRE library dependencies. And that was exactly
     98 what dynamic database client loading was meant to avoid. </p>
     99  
    100 </blockquote>
    101 
    102 <h2>Things to know</h2>
    103 
    104 <ul>
    105 
    106 <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,
    107 each pattern is applied to the entire input string. Depending on
    108 the application, that string is an entire client hostname, an entire
    109 client IP address, or an entire mail address. Thus, no parent domain
    110 or parent network search is done, "user@domain" mail addresses are
    111 not broken up into their user and domain constituent parts, and
    112 "user+foo" is not broken up into user and foo.  </p>
    113 
    114 <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
    115 not allowed to do $number substitution in lookup results that can
    116 be security sensitive: currently, that restriction applies to the
    117 local <a href="aliases.5.html">aliases(5)</a> database or the <a href="virtual.8.html">virtual(8)</a> delivery agent tables.
    118 </p>
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    120 </ul>
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