UNIX ON-LINE Man Pages - Die Onlinehilfe

Die Syntax von Unixbefehlen wird in den entsprechenden Manpages dokumentiert. Hier können Sie diese Onlinehilfe für viele Standardbefehle abrufen.

Suchoptionen:
Seiten auflisten, welche beginnen mit:
A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z   ALPHA   NUM   ANDERE   ALLE
XML::LibXML::XPathContUser3Contributed Perl DocumeXML::LibXML::XPathContext(3)

NAME
       XML::LibXML::XPathContext - XPath Evaluation

SYNOPSIS
         my $xpc = XML::LibXML::XPathContext->new();
         my $xpc = XML::LibXML::XPathContext->new($node);
         $xpc->registerNs($prefix, $namespace_uri)
         $xpc->unregisterNs($prefix)
         $uri = $xpc->lookupNs($prefix)
         $xpc->registerVarLookupFunc($callback, $data)
         $data = $xpc->getVarLookupData();
         $callback = $xpc->getVarLookupFunc();
         $xpc->unregisterVarLookupFunc($name);
         $xpc->registerFunctionNS($name, $uri, $callback)
         $xpc->unregisterFunctionNS($name, $uri)
         $xpc->registerFunction($name, $callback)
         $xpc->unregisterFunction($name)
         @nodes = $xpc->findnodes($xpath)
         @nodes = $xpc->findnodes($xpath, $context_node )
         $nodelist = $xpc->findnodes($xpath, $context_node )
         $object = $xpc->find($xpath )
         $object = $xpc->find($xpath, $context_node )
         $value = $xpc->findvalue($xpath )
         $value = $xpc->findvalue($xpath, $context_node )
         $bool = $xpc->exists( $xpath_expression, $context_node );
         $xpc->setContextNode($node)
         my $node = $xpc->getContextNode;
         $xpc->setContextPosition($position)
         my $position = $xpc->getContextPosition;
         $xpc->setContextSize($size)
         my $size = $xpc->getContextSize;
         $xpc->setContextNode($node)
       The XML::LibXML::XPathContext class provides an almost complete interface to
       libxml2's XPath implementation. With XML::LibXML::XPathContext is is possible
       to evaluate XPath expressions in the context of arbitrary node, context size,
       and context position, with a user-defined namespace-prefix mapping, custom
       XPath functions written in Perl, and even a custom XPath variable resolver.

EXAMPLES
   Namespaces
       This example demonstrates "registerNs()" method. It finds all paragraph
       nodes in an XHTML document.

         my $xc = XML::LibXML::XPathContext->new($xhtml_doc);
         $xc->registerNs('xhtml', 'http://www.w3.org/1999/xhtml');
         my @nodes = $xc->findnodes('//xhtml:p');

   Custom XPath functions
       This example demonstrates "registerFunction()" method by defining a
       function filtering nodes based on a Perl regular expression:

         sub grep_nodes {
           my ($nodelist,$regexp) =  @_;
           my $result = XML::LibXML::NodeList->new;
           for my $node ($nodelist->get_nodelist()) {
             $result->push($node) if $node->textContent =~ $regexp;
           }
           return $result;
         };

         my $xc = XML::LibXML::XPathContext->new($node);
         $xc->registerFunction('grep_nodes', \&grep_nodes);
         my @nodes = $xc->findnodes('//section[grep_nodes(para,"\bsearch(ing|es)?\b")]');

   Variables
       This example demonstrates "registerVarLookup()" method. We use XPath
       variables to recycle results of previous evaluations:

         sub var_lookup {
           my ($varname,$ns,$data)=@_;
           return $data->{$varname};
         }

         my $areas = XML::LibXML->new->parse_file('areas.xml');
         my $empl = XML::LibXML->new->parse_file('employees.xml');

         my $xc = XML::LibXML::XPathContext->new($empl);

         my %variables = (
           A => $xc->find('/employees/employee[@salary>10000]'),
           B => $areas->find('/areas/area[district='Brooklyn']/street'),
         );

         # get names of employees from $A working in an area listed in $B
         $xc->registerVarLookupFunc(\&var_lookup, \%variables);
         my @nodes = $xc->findnodes('$A[work_area/street = $B]/name');

METHODS
       new
             my $xpc = XML::LibXML::XPathContext->new();

           Creates a new XML::LibXML::XPathContext object without a context
           node.

             my $xpc = XML::LibXML::XPathContext->new($node);

           Creates a new XML::LibXML::XPathContext object with the context
           node set to $node.

       registerNs
             $xpc->registerNs($prefix, $namespace_uri)

           Registers namespace $prefix to $namespace_uri.

       unregisterNs
             $xpc->unregisterNs($prefix)

           Unregisters namespace $prefix.

       lookupNs
             $uri = $xpc->lookupNs($prefix)

           Returns namespace URI registered with $prefix. If $prefix is not
           registered to any namespace URI returns "undef".

       registerVarLookupFunc
             $xpc->registerVarLookupFunc($callback, $data)

           Registers variable lookup function $prefix. The registered function
           is executed by the XPath engine each time an XPath variable is
           evaluated. It takes three arguments: $data, variable name, and
           variable ns-URI and must return one value: a number or string or
           any "XML::LibXML::" object that can be a result of findnodes:
           Boolean, Literal, Number, Node (e.g.  Document, Element, etc.), or
           NodeList. For convenience, simple (non-blessed) array references
           containing only XML::LibXML::Node objects can be used instead of a
           XML::LibXML::NodeList.

       getVarLookupData
             $data = $xpc->getVarLookupData();

           Returns the data that have been associated with a variable lookup
           function during a previous call to "registerVarLookupFunc".

       getVarLookupFunc
             $callback = $xpc->getVarLookupFunc();

           Returns the variable lookup function previously registered with
           "registerVarLookupFunc".

       unregisterVarLookupFunc
             $xpc->unregisterVarLookupFunc($name);

           Unregisters variable lookup function and the associated lookup
           data.

       registerFunctionNS
             $xpc->registerFunctionNS($name, $uri, $callback)

           Registers an extension function $name in $uri namespace. $callback
           must be a CODE reference. The arguments of the callback function
           are either simple scalars or "XML::LibXML::*" objects depending on
           the XPath argument types. The function is responsible for checking
           the argument number and types. Result of the callback code must be
           a single value of the following types: a simple scalar (number,
           string) or an arbitrary "XML::LibXML::*" object that can be a
           result of findnodes: Boolean, Literal, Number, Node (e.g.
           Document, Element, etc.), or NodeList. For convenience, simple
           (non-blessed) array references containing only XML::LibXML::Node
           objects can be used instead of a XML::LibXML::NodeList.

       unregisterFunctionNS
             $xpc->unregisterFunctionNS($name, $uri)

           Unregisters extension function $name in $uri namespace. Has the
           same effect as passing "undef" as $callback to registerFunctionNS.

       registerFunction
             $xpc->registerFunction($name, $callback)

           Same as "registerFunctionNS" but without a namespace.

       unregisterFunction
             $xpc->unregisterFunction($name)

           Same as "unregisterFunctionNS" but without a namespace.

       findnodes
             @nodes = $xpc->findnodes($xpath)

             @nodes = $xpc->findnodes($xpath, $context_node )

             $nodelist = $xpc->findnodes($xpath, $context_node )

           Performs the xpath statement on the current node and returns the
           result as an array. In scalar context returns a
           XML::LibXML::NodeList object. Optionally, a node may be passed as a
           second argument to set the context node for the query.

           The xpath expression can be passed either as a string or or as a
           XML::LibXML::XPathExpression object.

       find
             $object = $xpc->find($xpath )

             $object = $xpc->find($xpath, $context_node )

           Performs the xpath expression using the current node as the context
           of the expression, and returns the result depending on what type of
           result the XPath expression had. For example, the XPath "1 * 3 +
           52" results in a XML::LibXML::Number object being returned. Other
           expressions might return a XML::LibXML::Boolean object, or a
           XML::LibXML::Literal object (a string). Each of those objects uses
           Perl's overload feature to ``do the right thing'' in different
           contexts. Optionally, a node may be passed as a second argument to
           set the context node for the query.

           The xpath expression can be passed either as a string or or as a
           XML::LibXML::XPathExpression object.

       findvalue
             $value = $xpc->findvalue($xpath )

             $value = $xpc->findvalue($xpath, $context_node )

           Is exactly equivalent to:

             $xpc->find( $xpath, $context_node )->to_literal;

           That is, it returns the literal value of the results. This enables
           you to ensure that you get a string back from your search, allowing
           certain shortcuts.  This could be used as the equivalent of
           <xsl:value-of select=``some_xpath''/>.  Optionally, a node may be
           passed in the second argument to set the context node for the
           query.

           The xpath expression can be passed either as a string or or as a
           XML::LibXML::XPathExpression object.

       exists
             $bool = $xpc->exists( $xpath_expression, $context_node );

           This method behaves like findnodes, except that it only returns a
           boolean value (1 if the expression matches a node, 0 otherwise) and
           may be faster than findnodes, because the XPath evaluation may stop
           early on the first match (this is true for libxml2 >= 2.6.27).

           For XPath expressions that do not return node-set, the method
           returns true if the returned value is a non-zero number or a non-
           empty string.

       setContextNode
             $xpc->setContextNode($node)

           Set the current context node.

       getContextNode
             my $node = $xpc->getContextNode;

           Get the current context node.

       setContextPosition
             $xpc->setContextPosition($position)

           Set the current context position. By default, this value is -1 (and
           evaluating XPath function "position()" in the initial context
           raises an XPath error), but can be set to any value up to context
           size. This usually only serves to cheat the XPath engine to return
           given position when "position()" XPath function is called. Setting
           this value to -1 restores the default behavior.

       getContextPosition
             my $position = $xpc->getContextPosition;

           Get the current context position.

       setContextSize
             $xpc->setContextSize($size)

           Set the current context size. By default, this value is -1 (and
           evaluating XPath function "last()" in the initial context raises an
           XPath error), but can be set to any non-negative value. This
           usually only serves to cheat the XPath engine to return the given
           value when "last()" XPath function is called. If context size is
           set to 0, position is automatically also set to 0. If context size
           is positive, position is automatically set to 1. Setting context
           size to -1 restores the default behavior.

       getContextSize
             my $size = $xpc->getContextSize;

           Get the current context size.

       setContextNode
             $xpc->setContextNode($node)

           Set the current context node.

BUGS AND CAVEATS
       XML::LibXML::XPathContext objects are reentrant, meaning that you can
       call methods of an XML::LibXML::XPathContext even from XPath extension
       functions registered with the same object or from a variable lookup
       function. On the other hand, you should rather avoid registering new
       extension functions, namespaces and a variable lookup function from
       within extension functions and a variable lookup function, unless you
       want to experience untested behavior.

AUTHORS
       Ilya Martynov and Petr Pajas, based on XML::LibXML and XML::LibXSLT
       code by Matt Sergeant and Christian Glahn.

HISTORICAL REMARK
       Prior to XML::LibXML 1.61 this module was distributed separately for
       maintenance reasons.

AUTHORS
       Matt Sergeant, Christian Glahn, Petr Pajas

VERSION
       1.70

COPYRIGHT
       2001-2007, AxKit.com Ltd.

       2002-2006, Christian Glahn.

       2006-2009, Petr Pajas.

perl v5.12.1                      2009-10-07      XML::LibXML::XPathContext(3)
 

Scannen Sie den Barcode um die Webseite zu öffnen


Quelle: http://www.trinler.net/de/service/doc/linux/man.html?command=XML%3A%3ALibXML%3A%3AXPathContext
Gedruckt am: 20.09.2017 04:07 GMT+0200 (2017-09-20T04:07:19+02:00)