how to use libxml2 to modify an existing xml file?

Question

I need to take an existing xml file, and modify just a few attributes and write the file back out.

I was thinking of using libxml2 to get this done. Application is C/C+

Answer 1

#include 
#include 
#include 

//Load in the xml file from disk
xmlDocPtr pDoc = xmlParseFile("file.xml");
//Or from a string xmlDocPtr pDoc = xmlNewDoc("");

//Do something with the document
//....

//Save the document back out to disk.
xmlSaveFileEnc("file.xml", pDoc, "UTF-8");

The main things you want are probably these functions:

xmlNodePtr pNode = xmlNewNode(0, (xmlChar*)"newNodeName");
xmlNodeSetContent(pNode, (xmlChar*)"content");
xmlAddChild(pParentNode, pNode);
xmlDocSetRootElement(pDoc, pParentNode);

And here is a quick example of using xpath to select things:

//Select all the user nodes
xmlChar *pExpression((xmlChar*)_T("/users/user"));
xmlXPathObjectPtr pResultingXPathObject(getnodeset(pDoc, pExpression));
if (pResultingXPathObject)
{
    xmlNodeSetPtr pNodeSet(pResultingXPathObject->nodesetval);
    for(int i = 0; i < pNodeSet->nodeNr; ++i) 
    {
        xmlNodePtr pUserNode(pNodeSet->nodeTab[i]);
                   //do something with the node
    }
}
xmlXPathFreeObject(pResultingXPathObject);