Libxml issue to get the attribute of a tag

Question

I want to get only the value of attribut Object but if don't work after the first node because it don't enter in the loop, why ?

This is my xml file:

     <msg><tag date="1557417027960" session="1697"><decision object="BAST04HEF" reliability="95" context="RO" x="796" y="371" 
 width="89" height="18" 
 direction="front"><jpeg></jpeg></decision></tag></msg>

And this my code:

int main(int argc, char **argv) {

  char         *docname;
  xmlDocPtr    doc;
  xmlNodePtr   cur;
  xmlChar      *object;

  if (argc < 2) {
    printf("Commande: %s nom_du_fichier\n", argv[0]);
    return EXIT_FAILURE;
  }


  docname = argv[1];

  doc = xmlParseFile(docname);
  cur = xmlDocGetRootElement(doc);

  cur = cur->xmlChildrenNode;
  while (cur != NULL) {
      if ((!xmlStrcmp(cur->name, (const xmlChar *)"decision"))) {
        object = xmlGetProp(cur, "object");
        printf("object: %s\n", object);
        xmlFree(object);
      }
      cur = cur->next;
  }
  xmlFreeDoc(doc);
  return EXIT_SUCCESS;
}

Answer 1

Your code processes only one level children, i.e. the direct children of the root element.

cur = xmlDocGetRootElement(doc); gets the root element.

cur = cur->xmlChildrenNode; gets the first (direct) child of the root element.

In you loop you get all siblings of this first child with cur = cur->next;, but you don't process their possible children.

Your XML snippet shows that you have at least three layers: msg - tag - decision.

If you want to process all decision elements regardless of what their parents are, you could use a recursive function.

static void processChildren(xmlNodePtr cur)

int main(int argc, char **argv) {

  char         *docname;
  xmlDocPtr    doc;
  xmlNodePtr   cur;
  xmlChar      *object;

  if (argc < 2) {
    printf("Commande: %s nom_du_fichier\n", argv[0]);
    return EXIT_FAILURE;
  }


  docname = argv[1];

  doc = xmlParseFile(docname);
  cur = xmlDocGetRootElement(doc);

  processChildren(cur->xmlChildrenNode);

  xmlFreeDoc(doc);
  return EXIT_SUCCESS;
}

static void processChildren(xmlNodePtr cur)
{
    while (cur != NULL) {
        if ((!xmlStrcmp(cur->name, (const xmlChar *)"decision"))) {
            object = xmlGetProp(cur, "object");
            printf("object: %s\n", object);
            xmlFree(object);
        }
        else
        {
            processChildren(cur->children);
        }
        cur = cur->next;
    }
}