Extracting XML node's text using XPath API in C

extract_xml_nodes_data.c

/**
 * This code is adapted from the sample available at:
 * http://xmlsoft.org/tutorial/apd.html.
 * 
 * Compile using the following command on linux/Mac:
 * gcc -lxml2 extract_xml_nodes_data.c -o xml_prog
 */

#include <libxml/parser.h>
#include <libxml/xpath.h>

xmlDocPtr load_xml_doc(char *xml_file_path) {
    xmlDocPtr doc = xmlParseFile(xml_file_path);
    if (doc == NULL) {
        fprintf(stderr, "ERROR: Document not parsed successfully. \n");
        return NULL;
    }
    return doc;
}

/**
 * Extract the nodes matching the given xpath from the supplied
 * XML document object.
 */
xmlXPathObjectPtr get_nodes_at_xpath(xmlDocPtr doc, xmlChar *xpath) {

    xmlXPathContextPtr context = xmlXPathNewContext(doc);
    if (context == NULL) {
        printf("ERROR: Failed to create xpath context from the XML document.\n");
        return NULL;
    }
    xmlXPathObjectPtr result = xmlXPathEvalExpression(xpath, context);
    xmlXPathFreeContext(context);
    if (result == NULL) {
        printf("ERROR: Failed to evaluate xpath expression.\n");
        return NULL;
    }
    if (xmlXPathNodeSetIsEmpty(result->nodesetval)) {
        xmlXPathFreeObject(result);
        printf("No matching nodes found at the xpath.\n");
        return NULL;
    }
    return result;
}

/**
 * Returns the text value of an XML element. It is expected that
 * there is only one XML element at the given xpath in the XML.
 */
xmlChar* get_element_text(char *node_xpath, xmlDocPtr doc) {
    xmlChar *node_text;
    xmlXPathObjectPtr result = get_nodes_at_xpath(doc, 
        (xmlChar*)node_xpath);
    if (result) {
        xmlNodeSetPtr nodeset = result->nodesetval;
        if (nodeset->nodeNr == 1) {
            node_text = xmlNodeListGetString(doc,
                nodeset->nodeTab[0]->xmlChildrenNode, 1);
        } else {
            printf("ERROR: Expected one %s node, found %d\n", node_xpath, nodeset->nodeNr);
        }
        xmlXPathFreeObject(result);
    } else {
        printf("ERROR: Node not found at xpath %s\n", node_xpath);
    }
    return node_text;
}

/**
 * Following XML sample is used to test this program.
 * 
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type='text/xsl'?>
<BMD>
    <Envelop>
        <MessageID>A9ECAEF2-107A-4452-9553-043B6D25386E</MessageID>
        <MessageType>CreditReport</MessageType>
        <Sender>756E2EAA-1D5B-4BC0-ACC4-4CEB669408DA</Sender>
        <Destination>6393F82F-4687-433D-AA23-1966330381FE</Destination>
        <CreationDateTime>2020-08-12T05:18:00+0000</CreationDateTime>
        <Signature>63f5f61f7a79301f715433f8f3689390d1f5da4f855169023300491c00b8113c</Signature>
        <ReferenceID>INV-PROFILE-889712</ReferenceID>
        <UserProperties>
            <key1>Value1</key1>
            <key2>Value2</key2>
        </UserProperties>
    </Envelop>
    <Payload>001-01-1234</Payload>
</BMD>

Output expected is:
    MessageID=A9ECAEF2-107A-4452-9553-043B6D25386E
    Sender=756E2EAA-1D5B-4BC0-ACC4-4CEB669408DA
    Destination=6393F82F-4687-433D-AA23-1966330381FE
    MessageType=CreditReport
    Payload=001-01-1234
*/
int main(int argc, char **argv) {
    char *docname = "/Users/someuser/temp/NHO2020/swan/esb_app/src/bmd_extract/recieved_bmd.xml";
    xmlDocPtr doc = load_xml_doc(docname);
    printf("MessageID=%s\n", get_element_text("//MessageID", doc));
    printf("Sender=%s\n", get_element_text("//Sender", doc));
    printf("Destination=%s\n", get_element_text("//Destination", doc));
    printf("MessageType=%s\n", get_element_text("//MessageType", doc));
    printf("Payload=%s\n", get_element_text("//Payload", doc));
    xmlFreeDoc(doc);
    xmlCleanupParser();
    return 1;
}