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.\" ========================================================================
.\"
.IX Title "XML::LibXML::Pattern 3"
.TH XML::LibXML::Pattern 3 "2021-04-17" "perl v5.26.3" "User Contributed Perl Documentation"
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.SH "NAME"
XML::LibXML::Pattern \- XML::LibXML::Pattern \- interface to libxml2 XPath patterns
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 3
\&  use XML::LibXML;
\&  my $pattern = XML::LibXML::Pattern\->new(\*(Aq/x:html/x:body//x:div\*(Aq, { \*(Aqx\*(Aq => \*(Aqhttp://www.w3.org/1999/xhtml\*(Aq });
\&  # test a match on an XML::LibXML::Node $node
\&
\&  if ($pattern\->matchesNode($node)) { ... }
\&
\&  # or on an XML::LibXML::Reader
\&
\&  if ($reader\->matchesPattern($pattern)) { ... }
\&
\&  # or skip reading all nodes that do not match
\&
\&  print $reader\->nodePath while $reader\->nextPatternMatch($pattern);
\&
\&  $pattern = XML::LibXML::Pattern\->new( pattern, { prefix => namespace_URI, ... } );
\&  $bool = $pattern\->matchesNode($node);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This is a perl interface to libxml2's pattern matching support \fIhttp://xmlsoft.org/html/libxml\-pattern.html\fR. This feature requires recent versions of libxml2.
.PP
Patterns are a small subset of XPath language, which is limited to
(disjunctions of) location paths involving the child and descendant axes in
abbreviated form as described by the extended \s-1BNF\s0 given below:
.PP
.Vb 4
\&  Selector ::=     Path ( \*(Aq|\*(Aq Path )*
\&  Path     ::=     (\*(Aq.//\*(Aq | \*(Aq//\*(Aq | \*(Aq/\*(Aq )? Step ( \*(Aq/\*(Aq Step )*
\&  Step     ::=     \*(Aq.\*(Aq | NameTest
\&  NameTest ::=     QName | \*(Aq*\*(Aq | NCName \*(Aq:\*(Aq \*(Aq*\*(Aq
.Ve
.PP
For readability, whitespace may be used in selector XPath expressions even
though not explicitly allowed by the grammar: whitespace may be freely added
within patterns before or after any token, where
.PP
.Vb 1
\&  token     ::=     \*(Aq.\*(Aq | \*(Aq/\*(Aq | \*(Aq//\*(Aq | \*(Aq|\*(Aq | NameTest
.Ve
.PP
Note that no predicates or attribute tests are allowed.
.PP
Patterns are particularly useful for stream parsing provided via the \f(CW\*(C`XML::LibXML::Reader\*(C'\fR interface.
.IP "\fBnew()\fR" 4
.IX Item "new()"
.Vb 1
\&  $pattern = XML::LibXML::Pattern\->new( pattern, { prefix => namespace_URI, ... } );
.Ve
.Sp
The constructor of a pattern takes a pattern expression (as described by the
\&\s-1BNF\s0 grammar above) and an optional \s-1HASH\s0 reference mapping prefixes to namespace
URIs. The method returns a compiled pattern object.
.Sp
Note that if the document has a default namespace, it must still be given an
prefix in order to be matched (as demanded by the XPath 1.0 specification). For
example, to match an element \f(CW\*(C`<a xmlns="http://foo.bar"</a>\*(C'\fR, one should use a pattern like this:
.Sp
.Vb 1
\&  $pattern = XML::LibXML::Pattern\->new( \*(Aqfoo:a\*(Aq, { foo => \*(Aqhttp://foo.bar\*(Aq });
.Ve
.IP "matchesNode($node)" 4
.IX Item "matchesNode($node)"
.Vb 1
\&  $bool = $pattern\->matchesNode($node);
.Ve
.Sp
Given an XML::LibXML::Node object, returns a true value if the node is matched
by the compiled pattern expression.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
XML::LibXML::Reader for other methods involving compiled patterns.
.SH "AUTHORS"
.IX Header "AUTHORS"
Matt Sergeant,
Christian Glahn,
Petr Pajas
.SH "VERSION"
.IX Header "VERSION"
2.0207
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
2001\-2007, AxKit.com Ltd.
.PP
2002\-2006, Christian Glahn.
.PP
2006\-2009, Petr Pajas.
.SH "LICENSE"
.IX Header "LICENSE"
This program is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.