As discussed before, nodes can have name and value, both of which are strings. Depending on node type, name or value may be absent. node_document nodes do not have a name or value, node_element and node_declaration nodes always have a name but never have a value, node_pcdata, node_cdata, node_comment and node_doctype nodes never have a name but always have a value (it may be empty though), node_pi nodes always have a name and a value (again, value may be empty). In order to set node's name or value, you can use the following functions:

bool xml_node::set_name(const char_t* rhs);
bool xml_node::set_value(const char_t* rhs);

Both functions try to set the name/value to the specified string, and return the operation result. The operation fails if the node can not have name or value (for instance, when trying to call set_name on a node_pcdata node), if the node handle is null, or if there is insufficient memory to handle the request. The provided string is copied into document managed memory and can be destroyed after the function returns (for example, you can safely pass stack-allocated buffers to these functions). The name/value content is not verified, so take care to use only valid XML names, or the document may become malformed.

There is no equivalent of child_value function for modifying text children of the node.

This is an example of setting node name and value (samples/modify_base.cpp):

pugi::xml_node node = doc.child("node");

// change node name
std::cout << node.set_name("notnode");
std::cout << ", new node name: " << node.name() << std::endl;

// change comment text
std::cout << doc.last_child().set_value("useless comment");
std::cout << ", new comment text: " << doc.last_child().value() << std::endl;

// we can't change value of the element or name of the comment
std::cout << node.set_value("1") << ", " << doc.last_child().set_name("2") << std::endl;

All attributes have name and value, both of which are strings (value may be empty). You can set them with the following functions:

bool xml_attribute::set_name(const char_t* rhs);
bool xml_attribute::set_value(const char_t* rhs);

Both functions try to set the name/value to the specified string, and return the operation result. The operation fails if the attribute handle is null, or if there is insufficient memory to handle the request. The provided string is copied into document managed memory and can be destroyed after the function returns (for example, you can safely pass stack-allocated buffers to these functions). The name/value content is not verified, so take care to use only valid XML names, or the document may become malformed.

In addition to string functions, several functions are provided for handling attributes with numbers and booleans as values:

bool xml_attribute::set_value(int rhs);
bool xml_attribute::set_value(unsigned int rhs);
bool xml_attribute::set_value(double rhs);
bool xml_attribute::set_value(bool rhs);
bool xml_attribute::set_value(long long rhs);
bool xml_attribute::set_value(unsigned long long rhs);

The above functions convert the argument to string and then call the base set_value function. Integers are converted to a decimal form, floating-point numbers are converted to either decimal or scientific form, depending on the number magnitude, boolean values are converted to either "true" or "false".

	Caution
	Number conversion functions depend on current C locale as set with setlocale, so may generate unexpected results if the locale is different from "C".

	Note
	set_value overloads with long long type are only available if your platform has reliable support for the type, including string conversions.

For convenience, all set_value functions have the corresponding assignment operators:

xml_attribute& xml_attribute::operator=(const char_t* rhs);
xml_attribute& xml_attribute::operator=(int rhs);
xml_attribute& xml_attribute::operator=(unsigned int rhs);
xml_attribute& xml_attribute::operator=(double rhs);
xml_attribute& xml_attribute::operator=(bool rhs);
xml_attribute& xml_attribute::operator=(long long rhs);
xml_attribute& xml_attribute::operator=(unsigned long long rhs);

These operators simply call the right set_value function and return the attribute they're called on; the return value of set_value is ignored, so errors are ignored.

This is an example of setting attribute name and value (samples/modify_base.cpp):

pugi::xml_attribute attr = node.attribute("id");

// change attribute name/value
std::cout << attr.set_name("key") << ", " << attr.set_value("345");
std::cout << ", new attribute: " << attr.name() << "=" << attr.value() << std::endl;

// we can use numbers or booleans
attr.set_value(1.234);
std::cout << "new attribute value: " << attr.value() << std::endl;

// we can also use assignment operators for more concise code
attr = true;
std::cout << "final attribute value: " << attr.value() << std::endl;

Nodes and attributes do not exist without a document tree, so you can't create them without adding them to some document. A node or attribute can be created at the end of node/attribute list or before/after some other node:

xml_attribute xml_node::append_attribute(const char_t* name);
xml_attribute xml_node::prepend_attribute(const char_t* name);
xml_attribute xml_node::insert_attribute_after(const char_t* name, const xml_attribute& attr);
xml_attribute xml_node::insert_attribute_before(const char_t* name, const xml_attribute& attr);

xml_node xml_node::append_child(xml_node_type type = node_element);
xml_node xml_node::prepend_child(xml_node_type type = node_element);
xml_node xml_node::insert_child_after(xml_node_type type, const xml_node& node);
xml_node xml_node::insert_child_before(xml_node_type type, const xml_node& node);

xml_node xml_node::append_child(const char_t* name);
xml_node xml_node::prepend_child(const char_t* name);
xml_node xml_node::insert_child_after(const char_t* name, const xml_node& node);
xml_node xml_node::insert_child_before(const char_t* name, const xml_node& node);

append_attribute and append_child create a new node/attribute at the end of the corresponding list of the node the method is called on; prepend_attribute and prepend_child create a new node/attribute at the beginning of the list; insert_attribute_after, insert_attribute_before, insert_child_after and insert_attribute_before add the node/attribute before or after the specified node/attribute.

Attribute functions create an attribute with the specified name; you can specify the empty name and change the name later if you want to. Node functions with the type argument create the node with the specified type; since node type can't be changed, you have to know the desired type beforehand. Also note that not all types can be added as children; see below for clarification. Node functions with the name argument create the element node (node_element) with the specified name.

All functions return the handle to the created object on success, and null handle on failure. There are several reasons for failure:

Even if the operation fails, the document remains in consistent state, but the requested node/attribute is not added.

	Caution
	attribute() and child() functions do not add attributes or nodes to the tree, so code like node.attribute("id") = 123; will not do anything if node does not have an attribute with name "id". Make sure you're operating with existing attributes/nodes by adding them if necessary.

This is an example of adding new attributes/nodes to the document (samples/modify_add.cpp):

// add node with some name
pugi::xml_node node = doc.append_child("node");

// add description node with text child
pugi::xml_node descr = node.append_child("description");
descr.append_child(pugi::node_pcdata).set_value("Simple node");

// add param node before the description
pugi::xml_node param = node.insert_child_before("param", descr);

// add attributes to param node
param.append_attribute("name") = "version";
param.append_attribute("value") = 1.1;
param.insert_attribute_after("type", param.attribute("name")) = "float";

If you do not want your document to contain some node or attribute, you can remove it with one of the following functions:

bool xml_node::remove_attribute(const xml_attribute& a);
bool xml_node::remove_child(const xml_node& n);

remove_attribute removes the attribute from the attribute list of the node, and returns the operation result. remove_child removes the child node with the entire subtree (including all descendant nodes and attributes) from the document, and returns the operation result. Removing fails if one of the following is true:

Removing the attribute or node invalidates all handles to the same underlying object, and also invalidates all iterators pointing to the same object. Removing node also invalidates all past-the-end iterators to its attribute or child node list. Be careful to ensure that all such handles and iterators either do not exist or are not used after the attribute/node is removed.

If you want to remove the attribute or child node by its name, two additional helper functions are available:

bool xml_node::remove_attribute(const char_t* name);
bool xml_node::remove_child(const char_t* name);

These functions look for the first attribute or child with the specified name, and then remove it, returning the result. If there is no attribute or child with such name, the function returns false; if there are two nodes with the given name, only the first node is deleted. If you want to delete all nodes with the specified name, you can use code like this: while (node.remove_child("tool")) ;.

This is an example of removing attributes/nodes from the document (samples/modify_remove.cpp):

// remove description node with the whole subtree
pugi::xml_node node = doc.child("node");
node.remove_child("description");

// remove id attribute
pugi::xml_node param = node.child("param");
param.remove_attribute("value");

// we can also remove nodes/attributes by handles
pugi::xml_attribute id = param.attribute("name");
param.remove_attribute(id);

pugixml provides a special class, xml_text, to work with text contents stored as a value of some node, i.e. <node><description>This is a node</description></node>. Working with text objects to retrieve data is described in the documentation for accessing document data; this section describes the modification interface of xml_text.

Once you have an xml_text object, you can set the text contents using the following function:

bool xml_text::set(const char_t* rhs);

This function tries to set the contents to the specified string, and returns the operation result. The operation fails if the text object was retrieved from a node that can not have a value and is not an element node (i.e. it is a node_declaration node), if the text object is empty, or if there is insufficient memory to handle the request. The provided string is copied into document managed memory and can be destroyed after the function returns (for example, you can safely pass stack-allocated buffers to this function). Note that if the text object was retrieved from an element node, this function creates the PCDATA child node if necessary (i.e. if the element node does not have a PCDATA/CDATA child already).

In addition to a string function, several functions are provided for handling text with numbers and booleans as contents:

bool xml_text::set(int rhs);
bool xml_text::set(unsigned int rhs);
bool xml_text::set(double rhs);
bool xml_text::set(bool rhs);
bool xml_text::set(long long rhs);
bool xml_text::set(unsigned long long rhs);

The above functions convert the argument to string and then call the base set function. These functions have the same semantics as similar xml_attribute functions. You can refer to documentation for the attribute functions for details.

For convenience, all set functions have the corresponding assignment operators:

xml_text& xml_text::operator=(const char_t* rhs);
xml_text& xml_text::operator=(int rhs);
xml_text& xml_text::operator=(unsigned int rhs);
xml_text& xml_text::operator=(double rhs);
xml_text& xml_text::operator=(bool rhs);
xml_text& xml_text::operator=(long long rhs);
xml_text& xml_text::operator=(unsigned long long rhs);

These operators simply call the right set function and return the attribute they're called on; the return value of set is ignored, so errors are ignored.

This is an example of using xml_text object to modify text contents (samples/text.cpp):

// change project version
project.child("version").text() = 1.2;

// add description element and set the contents
// note that we do not have to explicitly add the node_pcdata child
project.append_child("description").text().set("a test project");

With the help of previously described functions, it is possible to create trees with any contents and structure, including cloning the existing data. However since this is an often needed operation, pugixml provides built-in node/attribute cloning facilities. Since nodes and attributes do not exist without a document tree, you can't create a standalone copy - you have to immediately insert it somewhere in the tree. For this, you can use one of the following functions:

xml_attribute xml_node::append_copy(const xml_attribute& proto);
xml_attribute xml_node::prepend_copy(const xml_attribute& proto);
xml_attribute xml_node::insert_copy_after(const xml_attribute& proto, const xml_attribute& attr);
xml_attribute xml_node::insert_copy_before(const xml_attribute& proto, const xml_attribute& attr);

xml_node xml_node::append_copy(const xml_node& proto);
xml_node xml_node::prepend_copy(const xml_node& proto);
xml_node xml_node::insert_copy_after(const xml_node& proto, const xml_node& node);
xml_node xml_node::insert_copy_before(const xml_node& proto, const xml_node& node);

These functions mirror the structure of append_child, prepend_child, insert_child_before and related functions - they take the handle to the prototype object, which is to be cloned, insert a new attribute/node at the appropriate place, and then copy the attribute data or the whole node subtree to the new object. The functions return the handle to the resulting duplicate object, or null handle on failure.

The attribute is copied along with the name and value; the node is copied along with its type, name and value; additionally attribute list and all children are recursively cloned, resulting in the deep subtree clone. The prototype object can be a part of the same document, or a part of any other document.

The failure conditions resemble those of append_child, insert_child_before and related functions, consult their documentation for more information. There are additional caveats specific to cloning functions:

This is an example with one possible implementation of include tags in XML (samples/include.cpp). It illustrates node cloning and usage of other document modification functions:

bool load_preprocess(pugi::xml_document& doc, const char* path);

bool preprocess(pugi::xml_node node)
{
    for (pugi::xml_node child = node.first_child(); child; )
    {
        if (child.type() == pugi::node_pi && strcmp(child.name(), "include") == 0)
        {
            pugi::xml_node include = child;

            // load new preprocessed document (note: ideally this should handle relative paths)
            const char* path = include.value();

            pugi::xml_document doc;
            if (!load_preprocess(doc, path)) return false;

            // insert the comment marker above include directive
            node.insert_child_before(pugi::node_comment, include).set_value(path);

            // copy the document above the include directive (this retains the original order!)
            for (pugi::xml_node ic = doc.first_child(); ic; ic = ic.next_sibling())
            {
                node.insert_copy_before(ic, include);
            }

            // remove the include node and move to the next child
            child = child.next_sibling();

            node.remove_child(include);
        }
        else
        {
            if (!preprocess(child)) return false;

            child = child.next_sibling();
        }
    }

    return true;
}

bool load_preprocess(pugi::xml_document& doc, const char* path)
{
    pugi::xml_parse_result result = doc.load_file(path, pugi::parse_default | pugi::parse_pi); // for <?include?>
    
    return result ? preprocess(doc) : false;
}

Sometimes instead of cloning a node you need to move an existing node to a different position in a tree. This can be accomplished by copying the node and removing the original; however, this is expensive since it results in a lot of extra operations. For moving nodes within the same document tree, you can use of the following functions instead:

xml_node xml_node::append_move(const xml_node& moved);
xml_node xml_node::prepend_move(const xml_node& moved);
xml_node xml_node::insert_move_after(const xml_node& moved, const xml_node& node);
xml_node xml_node::insert_move_before(const xml_node& moved, const xml_node& node);

These functions mirror the structure of append_copy, prepend_copy, insert_copy_before and insert_copy_after - they take the handle to the moved object and move it to the appropriate place with all attributes and/or child nodes. The functions return the handle to the resulting object (which is the same as the moved object), or null handle on failure.

The failure conditions resemble those of append_child, insert_child_before and related functions, consult their documentation for more information. There are additional caveats specific to moving functions:

pugixml provides several ways to assemble an XML document from other XML documents. Assuming there is a set of document fragments, represented as in-memory buffers, the implementation choices are as follows:

bool append_fragment(pugi::xml_node target, const char* buffer, size_t size)
{
    pugi::xml_document doc;
    if (!doc.load_buffer(buffer, size)) return false;

    for (pugi::xml_node child = doc.first_child(); child; child = child.next_sibling())
        target.append_copy(child);
}

bool append_fragment(pugi::xml_node target, const pugi::xml_document& cached_fragment)
{
    for (pugi::xml_node child = cached_fragment.first_child(); child; child = child.next_sibling())
        target.append_copy(child);
}

xml_parse_result xml_node::append_buffer(const void* contents, size_t size, unsigned int options = parse_default, xml_encoding encoding = encoding_auto);

The first method is more convenient, but slower than the other two. The relative performance of append_copy and append_buffer depends on the buffer format - usually append_buffer is faster if the buffer is in native encoding (UTF-8 or wchar_t, depending on PUGIXML_WCHAR_MODE). At the same time it might be less efficient in terms of memory usage - the implementation makes a copy of the provided buffer, and the copy has the same lifetime as the document - the memory used by that copy will be reclaimed after the document is destroyed, but no sooner. Even deleting all nodes in the document, including the appended ones, won't reclaim the memory.

append_buffer behaves in the same way as xml_document::load_buffer - the input buffer is a byte buffer, with size in bytes; the buffer is not modified and can be freed after the function returns.

Since append_buffer needs to append child nodes to the current node, it only works if the current node is either document or element node. Calling append_buffer on a node with any other type results in an error with status_append_invalid_root status.