diff --git a/CHANGELOG.md b/CHANGELOG.md
index f6fd5f4f..b6977be6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@
       <CLICON_FEATURE>*:*</CLICON_FEATURE>
 ```
   * logical combination of features not implemented, eg if-feature "not foo or bar and baz";
+  * ietf-netconf yang module added with candidate, validate, startup and xpath features enabled.
 * YANG Module Library support
   * According to RFC 7895 and implemented by ietf-yang-library.yang
   * Changed Netconf hello to single capabilty urn:ietf:params:netconf:capability:yang-library:1.0 according to YANG 1.1 RFC7950 Sec 5.6.4.
@@ -32,7 +33,8 @@
 
 ### API changes on existing features (you may need to change your code)
 * Netconf hello capability updated to YANG 1.1 RFC7950 Sec 5.6.4
-  * A single capability is announced instead of many.
+  * Added urn:ietf:params:netconf:capability:yang-library:1.0
+  * Thanks SCadilhac for helping out, see https://github.com/clicon/clixon/issues/39
 * Major rewrite of event streams
   * If you used old event callbacks API, you need to switch to the streams API
     * See clixon_stream.[ch]
@@ -72,8 +74,8 @@
 	goto done;
 ```    
 
-
 ### Minor changes
+* uri_percent_encode() and xml_chardata_encode() changed to stdarg parameters
 * Added CLIXON_DEFAULT_CONFIG=/usr/local/etc/clixon.xml as option and in example (so you dont need to provide -f command-line option).
 * Yang 1.1 action syntax added (but function is not supported)
 * New function: clicon_conf_xml() returns configuration tree
diff --git a/apps/backend/backend_main.c b/apps/backend/backend_main.c
index efa705fe..391ecffd 100644
--- a/apps/backend/backend_main.c
+++ b/apps/backend/backend_main.c
@@ -751,6 +751,9 @@ main(int    argc,
      /* Load yang module library, RFC7895 */
     if (yang_modules_init(h) < 0)
 	goto done;
+    /* Add netconf yang spec, used by netconf client and as internal protocol */
+    if (netconf_module_load(h) < 0)
+	goto done;
     /* Load yang Restconf stream discovery */
      if (clicon_option_bool(h, "CLICON_STREAM_DISCOVERY_RFC8040") &&
 	 yang_spec_parse_module(h, "ietf-restconf-monitoring", CLIXON_DATADIR, NULL, yspec)< 0)
diff --git a/apps/cli/cli_main.c b/apps/cli/cli_main.c
index c63b6e98..40f27d6e 100644
--- a/apps/cli/cli_main.c
+++ b/apps/cli/cli_main.c
@@ -432,6 +432,9 @@ main(int argc, char **argv)
 				    clicon_yang_module_revision(h),
 				    yspec) < 0)
 	goto done;
+     /* Load yang module library, RFC7895 */
+    if (yang_modules_init(h) < 0)
+	goto done;
     if (printspec)
 	yang_print(stdout, (yang_node*)yspec);
 
diff --git a/apps/netconf/netconf_hello.c b/apps/netconf/netconf_hello.c
index 6343a299..61803c3b 100644
--- a/apps/netconf/netconf_hello.c
+++ b/apps/netconf/netconf_hello.c
@@ -106,12 +106,46 @@ netconf_hello_dispatch(cxobj *xn)
 }
 
 /*! Create Netconf hello. Single cap and defer individual to querying modules
- * This follows YANG 1.1 RFC7950 Sec 5.6.4, where a single capability announced
- * and a client may query supported modules using RFC 7895 (Yang Module 
- * Library).
+
  * @param[in]  h           Clicon handle
  * @param[in]  cb          Msg buffer
  * @param[in]  session_id  Id of client session
+ * Lots of dependencies here. regarding the hello protocol.
+ * RFC6241 NETCONF Protocol says: (8.1)
+ *    MUST send a <hello> element containing a list of that peer's capabilities
+ *    MUST send at least the base NETCONF capability, urn:ietf:params:netconf:base:1.1
+ *    MAY include capabilities for previous NETCONF versions
+ *    MUST include a <session-id>
+ * the example shows urn:ietf:params:netconf:capability:startup:1.0 
+
+ * RFC5277 NETCONF Event Notifications
+ *  urn:ietf:params:netconf:capability:notification:1.0 is advertised during the capability exchange
+ *  
+ * RFC6022 YANG Module for NETCONF Monitoring
+ *     MUST advertise the capability URI "urn:ietf:params:xml:ns:yang:ietf-netconf-monitoring"
+ * RFC7895 Yang module library defines how to announce module features (not hell capabilities)
+ * RFC7950 YANG 1.1 says (5.6.4);
+ *    MUST announce the modules it implements by implementing the YANG module 
+ *    "ietf-yang-library" (RFC7895) and listing all implemented modules in the
+ *    "/modules-state/module" list.
+ *    MUST advertise urn:ietf:params:netconf:capability:yang-library:1.0?
+ *    revision=<date>&module-set-id=<id> in the <hello> message.
+ *
+ * Question: should the NETCONF in RFC6241 sections 8.2-8.9 be announced both 
+ * as features and as capabilities in the <hello> message according to RFC6241?
+ *   urn:ietf:params:netconf:capability:candidate:1:0 (8.3)
+ *   urn:ietf:params:netconf:capability:validate:1.1 (8.6)
+ *   urn:ietf:params:netconf:capability:startup:1.0 (8.7)
+ *   urn:ietf:params:netconf:capability:xpath:1.0 (8.9)
+ *   urn:ietf:params:netconf:capability:notification:1.0 (RFC5277)
+ *
+ * @note the hello message is created bythe netconf application, not the 
+ *  backend, and backend may implement more modules - please consider if using
+ *  library routines for detecting capabilities here. In contrast, yang module 
+ * list (RFC7895) is processed by the backend.
+ * @note encode bodies, see xml_chardata_encode()
+ * @see yang_modules_state_get
+ * @see netconf_module_load
  */
 int
 netconf_create_hello(clicon_handle h,
@@ -121,21 +155,27 @@ netconf_create_hello(clicon_handle h,
     int   retval = -1;
     char *module_set_id;
     char *ietf_yang_library_revision;
+    char *encstr = NULL;
 
     module_set_id = clicon_option_str(h, "CLICON_MODULE_SET_ID");
     if ((ietf_yang_library_revision = yang_modules_revision(h)) == NULL)
 	goto done;
     add_preamble(cb);
-    cprintf(cb, "<hello>");
+    cprintf(cb, "<hello xmlns=\"urn:ietf:params:xml:ns:netconf:base:1.0\">");
     cprintf(cb, "<capabilities>");
-    cprintf(cb, "<capability>urn:ietf:params:netconf:capability:yang-library:1.0?revision=\"%s\"&module-set-id=%s</capability>",
-	    ietf_yang_library_revision,
-	    module_set_id);
-      cprintf(cb, "</capabilities>");
+        cprintf(cb, "<capability>urn:ietf:params:netconf:base:1.1</capability>");
+    if (xml_chardata_encode(&encstr, "urn:ietf:params:netconf:capability:yang-library:1.0?revision=\"%s\"&module-set-id=%s",
+			    ietf_yang_library_revision,
+			    module_set_id) < 0)
+	goto done;
+    cprintf(cb, "<capability>%s</capability>", encstr);
+    cprintf(cb, "</capabilities>");
     cprintf(cb, "<session-id>%lu</session-id>", (long unsigned int)42+session_id);
     cprintf(cb, "</hello>");
     add_postamble(cb);
     retval = 0;
  done:
+    if (encstr)
+	free(encstr);
     return retval;
 }
diff --git a/apps/netconf/netconf_lib.c b/apps/netconf/netconf_lib.c
index 998b4ef0..fc24810b 100644
--- a/apps/netconf/netconf_lib.c
+++ b/apps/netconf/netconf_lib.c
@@ -182,6 +182,9 @@ netconf_get_target(cxobj        *xn,
  * @param[in]   s    
  * @param[in]   cb   Cligen buffer that contains the XML message
  * @param[in]   msg  Only for debug
+ * @note Assumes "cb" contains valid XML, ie encoding is correct. This is done
+ *       if it is output by a xml render routine (xml_print et al), but NOT
+ *       otherwise.
  */
 int 
 netconf_output(int   s, 
diff --git a/apps/netconf/netconf_main.c b/apps/netconf/netconf_main.c
index 7e7a279c..804902df 100644
--- a/apps/netconf/netconf_main.c
+++ b/apps/netconf/netconf_main.c
@@ -432,9 +432,11 @@ main(int    argc,
     argc -= optind;
     argv += optind;
 
+    /* Create first yang spec */
     if ((yspec = yspec_new()) == NULL)
 	goto done;
     clicon_dbspec_yang_set(h, yspec);	
+
     /* Parse yang database spec file */
     if (yang_filename){
 	if (yang_spec_parse_file(h, yang_filename, clicon_yang_dir(h), yspec) < 0)
@@ -446,10 +448,12 @@ main(int    argc,
 				    yspec) < 0)
 	goto done;
     
+     /* Load yang module library, RFC7895 */
+    if (yang_modules_init(h) < 0)
+	goto done;
     /* Add netconf yang spec, used by netconf client and as internal protocol */
-    if (yang_spec_parse_module(h, "ietf-yang-library", CLIXON_DATADIR, NULL, yspec)< 0)
-	 goto done;
-
+    if (netconf_module_load(h) < 0)
+	goto done;
     /* Initialize plugins group */
     if ((dir = clicon_netconf_dir(h)) != NULL)
 	if (clixon_plugins_load(h, CLIXON_PLUGIN_INIT, dir, NULL) < 0)
diff --git a/apps/restconf/restconf_main.c b/apps/restconf/restconf_main.c
index aef61257..b107f6dd 100644
--- a/apps/restconf/restconf_main.c
+++ b/apps/restconf/restconf_main.c
@@ -635,6 +635,10 @@ main(int    argc,
 		       clicon_yang_module_revision(h),
 		       yspec) < 0)
 	goto done;
+
+     /* Load yang module library, RFC7895 */
+    if (yang_modules_init(h) < 0)
+	goto done;
     /* Add system modules */
      if (clicon_option_bool(h, "CLICON_STREAM_DISCOVERY_RFC8040") &&
 	 yang_spec_parse_module(h, "ietf-restconf-monitoring", CLIXON_DATADIR, NULL, yspec)< 0)
@@ -642,9 +646,7 @@ main(int    argc,
      if (clicon_option_bool(h, "CLICON_STREAM_DISCOVERY_RFC5277") &&
 	 yang_spec_parse_module(h, "ietf-netconf-notification", CLIXON_DATADIR, NULL, yspec)< 0)
 	 goto done;
-     /* Load yang module library, RFC7895 */
-    if (yang_modules_init(h) < 0)
-	goto done;
+
 
      if (stream_register(h, "NETCONF", "default NETCONF event stream") < 0)
 	goto done;
diff --git a/datastore/keyvalue/clixon_keyvalue.c b/datastore/keyvalue/clixon_keyvalue.c
index 4e77418d..39a11134 100644
--- a/datastore/keyvalue/clixon_keyvalue.c
+++ b/datastore/keyvalue/clixon_keyvalue.c
@@ -211,7 +211,7 @@ append_listkeys(cbuf      *ckey,
 		       xml_name(xt), keyname);
 	    goto done;
 	}
-	if (uri_percent_encode(xml_body(xkey), &bodyenc) < 0)
+	if (uri_percent_encode(&bodyenc, "%s", xml_body(xkey)) < 0)
 	    goto done;
 	if (i++)
 	    cprintf(ckey, ",");
@@ -328,7 +328,7 @@ get(char      *dbname,
 	     * If xml element is a leaf-list, then the next element is expected to
 	     * be a value
 	     */
-	    if (uri_percent_decode(restval, &argdec) < 0)
+	    if (uri_percent_decode(&argdec, restval) < 0)
 		goto done;
 	    if ((xc = xml_find(x, name))==NULL ||
 		(xb = xml_find(xc, argdec))==NULL){
@@ -681,7 +681,7 @@ put(char               *dbfile,
 	    goto done;
 	break;
     case Y_LEAF_LIST:
-	if (uri_percent_encode(body, &bodyenc) < 0)
+	if (uri_percent_encode(&bodyenc, "%s", body) < 0)
 	    goto done;
 	cprintf(cbxk, "=%s", bodyenc);
 	break;
diff --git a/lib/clixon/clixon_netconf_lib.h b/lib/clixon/clixon_netconf_lib.h
index 063345e3..cdf570e9 100644
--- a/lib/clixon/clixon_netconf_lib.h
+++ b/lib/clixon/clixon_netconf_lib.h
@@ -63,5 +63,6 @@ int netconf_operation_failed_xml(cxobj **xret, char *type, char *message);
 int netconf_malformed_message(cbuf *cb, char *message);
 int netconf_malformed_message_xml(cxobj **xret, char *message);
 int netconf_trymerge(cxobj *x, yang_spec *yspec, cxobj **xret);
+int netconf_module_load(clicon_handle h);
 
 #endif /* _CLIXON_NETCONF_LIB_H */
diff --git a/lib/clixon/clixon_string.h b/lib/clixon/clixon_string.h
index 5b5789dd..cebb0871 100644
--- a/lib/clixon/clixon_string.h
+++ b/lib/clixon/clixon_string.h
@@ -76,9 +76,14 @@ static inline char * strdup4(char *str)
 char **clicon_strsep(char *string, char *delim, int  *nvec0);
 char *clicon_strjoin (int argc, char **argv, char *delim);
 int str2cvec(char *string, char delim1, char delim2, cvec **cvp);
-int uri_percent_encode(char *str, char **escp);
-int uri_percent_decode(char *esc, char **str);
-int xml_chardata_encode(char *str, char **escp);
+#if defined(__GNUC__) && __GNUC__ >= 3
+int uri_percent_encode(char **encp, char *fmt, ...) __attribute__ ((format (printf, 2, 3)));
+int xml_chardata_encode(char **escp, char *fmt, ... ) __attribute__ ((format (printf, 2, 3)));
+#else
+int uri_percent_encode(char **encp, char *str, ...);
+int xml_chardata_encode(char **escp, char *fmt, ...);
+#endif
+int uri_percent_decode(char *enc, char **str);
 const char *clicon_int2str(const map_str2int *mstab, int i);
 int clicon_str2int(const map_str2int *mstab, char *str);
 
diff --git a/lib/src/clixon_netconf_lib.c b/lib/src/clixon_netconf_lib.c
index d59e88c9..9c4f3dca 100644
--- a/lib/src/clixon_netconf_lib.c
+++ b/lib/src/clixon_netconf_lib.c
@@ -86,7 +86,7 @@ netconf_in_use(cbuf *cb,
 		type) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -125,7 +125,7 @@ netconf_invalid_value(cbuf *cb,
 		type) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -165,7 +165,7 @@ netconf_too_big(cbuf *cb,
 		type) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -207,7 +207,7 @@ netconf_missing_attribute(cbuf *cb,
 		type, info) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -248,7 +248,7 @@ netconf_bad_attribute(cbuf *cb,
 		type, info) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -290,7 +290,7 @@ netconf_unknown_attribute(cbuf *cb,
 		type, info) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -332,7 +332,7 @@ netconf_missing_element(cbuf      *cb,
 		type, info) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -375,7 +375,7 @@ netconf_bad_element(cbuf *cb,
 		type, info) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -417,7 +417,7 @@ netconf_unknown_element(cbuf *cb,
 		type, info) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -459,7 +459,7 @@ netconf_unknown_namespace(cbuf *cb,
 		type, info) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -498,7 +498,7 @@ netconf_access_denied(cbuf *cb,
 		type) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -574,7 +574,7 @@ netconf_lock_denied(cbuf *cb,
 		info) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -613,7 +613,7 @@ netconf_resource_denied(cbuf *cb,
 		type) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -653,7 +653,7 @@ netconf_rollback_failed(cbuf *cb,
 		type) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -691,7 +691,7 @@ netconf_data_exists(cbuf      *cb,
 		"<error-severity>error</error-severity>") <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -729,7 +729,7 @@ netconf_data_missing(cbuf *cb,
 		"<error-severity>error</error-severity>") <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -769,7 +769,7 @@ netconf_operation_not_supported(cbuf *cb,
 		type) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -809,7 +809,7 @@ netconf_operation_failed(cbuf  *cb,
 		type) <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -884,7 +884,7 @@ netconf_malformed_message(cbuf  *cb,
 		"<error-severity>error</error-severity>") <0)
 	goto err;
     if (message){
-	if (xml_chardata_encode(message, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", message) < 0)
 	    goto done;
 	if (cprintf(cb, "<error-message>%s</error-message>", encstr) < 0)
 	    goto err;
@@ -970,3 +970,40 @@ netconf_trymerge(cxobj       *x,
 	free(reason);
     return retval;
 }
+
+/*! Load ietf netconf yang module and set enabled features
+ * The features added are:
+ *   candidate (8.3)
+ *   validate (8.6)
+ *   startup (8.7)
+ *   xpath (8.9)
+ */
+int
+netconf_module_load(clicon_handle h)
+{
+    int        retval = -1;
+    cxobj     *xc;
+    //    cxobj     *x;
+    yang_spec *yspec;
+
+    yspec = clicon_dbspec_yang(h);
+    /* Load yang spec */
+    if (yang_spec_parse_module(h, "ietf-netconf", CLIXON_DATADIR, NULL, yspec)< 0)
+	goto done;
+    if ((xc = clicon_conf_xml(h)) == NULL){
+	clicon_err(OE_CFG, ENOENT, "Clicon configuration not loaded");
+	goto done; 
+    }
+    /* Enable features (hardcoded here) */
+    if (xml_parse_string("<CLICON_FEATURE>ietf-netconf:candidate</CLICON_FEATURE>", yspec, &xc) < 0)
+	goto done;
+    if (xml_parse_string("<CLICON_FEATURE>ietf-netconf:validate</CLICON_FEATURE>", yspec, &xc) < 0)
+	goto done;
+    if (xml_parse_string("<CLICON_FEATURE>ietf-netconf:startup</CLICON_FEATURE>", yspec, &xc) < 0)
+	goto done;
+    if (xml_parse_string("<CLICON_FEATURE>ietf-netconf:xpath</CLICON_FEATURE>", yspec, &xc) < 0)
+	goto done;
+    retval = 0;
+ done:
+    return retval;
+}
diff --git a/lib/src/clixon_options.c b/lib/src/clixon_options.c
index 1c0584d9..9fb9e3af 100644
--- a/lib/src/clixon_options.c
+++ b/lib/src/clixon_options.c
@@ -249,8 +249,10 @@ clicon_options_main(clicon_handle h)
 	xml_child_sort = 0;
     retval = 0;
  done:
-    if (yspec) /* The clixon yang-spec is not used after this */
+#if 0 /* XXX yspec should be part of top-level yang but cant since it will be main module */
+	 if (yspec) 
 	yspec_free(yspec);
+#endif
     return retval;
 }
 
@@ -589,6 +591,7 @@ clicon_dbspec_yang_set(clicon_handle     h,
 
 /*! Get YANG specification for Clixon system options and features
  * Must use hash functions directly since they are not strings.
+ * Example: features are typically accessed directly in the config tree.
  */
 cxobj *
 clicon_conf_xml(clicon_handle h)
diff --git a/lib/src/clixon_string.c b/lib/src/clixon_string.c
index 655bc9f1..0b0f73dd 100644
--- a/lib/src/clixon_string.c
+++ b/lib/src/clixon_string.c
@@ -174,49 +174,77 @@ uri_unreserved(unsigned char in)
 }
 
 /*! Percent encoding according to RFC 3986 URI Syntax
- * @param[in]   str    Not-encoded input string     
- * @param[out]  escp   Encoded/escaped malloced output string
+ * @param[out]  encp   Encoded malloced output string
+ * @param[in]   fmt    Not-encoded input string (stdarg format string)
+ * @param[in]   ...    stdarg variable parameters
  * @retval      0      OK
  * @retval     -1      Error
+ * @code
+ *  char *enc;
+ *  if (uri_percent_encode(&enc, "formatstr: <>= %s", "substr<>") < 0)
+ *    err;
+ *  if(enc)
+ *    free(enc);
+ * @endcode
  * @see RFC 3986 Uniform Resource Identifier (URI): Generic Syntax
  * @see uri_percent_decode
  * @see xml_chardata_encode
  */
 int
-uri_percent_encode(char  *str, 
-		   char **escp)
+uri_percent_encode(char **encp, 
+		   char  *fmt, ...)
 {
-    int   retval = -1;
-    char *esc = NULL;
-    int   len;
-    int   i, j;
-    
+    int     retval = -1;
+    char   *str = NULL;  /* Expanded format string w stdarg */
+    char   *enc = NULL;
+    int     fmtlen;
+    int     len;
+    int     i, j;
+    va_list args;
+
+    /* Two steps: (1) read in the complete format string */
+    va_start(args, fmt); /* dryrun */
+    fmtlen = vsnprintf(NULL, 0, fmt, args) + 1;
+    va_end(args);
+    if ((str = malloc(fmtlen)) == NULL){
+	clicon_err(OE_UNIX, errno, "malloc");
+	goto done;
+    }
+    memset(str, 0, fmtlen);
+    va_start(args, fmt); /* real */
+    fmtlen = vsnprintf(str, fmtlen, fmt, args) + 1;
+    va_end(args);
+    /* Now str is the combined fmt + ... */
+
+    /* Step (2) encode and expand str --> enc */
     /* This is max */
     len = strlen(str)*3+1;
-    if ((esc = malloc(len)) == NULL){
+    if ((enc = malloc(len)) == NULL){
 	clicon_err(OE_UNIX, errno, "malloc"); 
 	goto done;
     }
-    memset(esc, 0, len);
+    memset(enc, 0, len);
     j = 0;
     for (i=0; i<strlen(str); i++){
 	if (uri_unreserved(str[i]))
-	    esc[j++] = str[i];
+	    enc[j++] = str[i];
 	else{
-	    snprintf(&esc[j], 4, "%%%02X", str[i]&0xff);
+	    snprintf(&enc[j], 4, "%%%02X", str[i]&0xff);
 	    j += 3;
 	}
     }
-    *escp = esc;
+    *encp = enc;
     retval = 0;
  done:
-    if (retval < 0 && esc)
-	free(esc);
+    if (str)
+	free(str);
+    if (retval < 0 && enc)
+	free(enc);
     return retval;
 }
 
 /*! Percent decoding according to RFC 3986 URI Syntax
- * @param[in]   esc    Escaped/encoded input string     
+ * @param[in]   enc    Encoded input string     
  * @param[out]  strp   Decoded malloced output string. Deallocate with free()
  * @retval      0      OK
  * @retval     -1      Error
@@ -224,7 +252,7 @@ uri_percent_encode(char  *str,
  * @see uri_percent_encode
  */
 int
-uri_percent_decode(char  *esc, 
+uri_percent_decode(char  *enc, 
 		   char **strp)
 {
     int   retval = -1;
@@ -235,24 +263,24 @@ uri_percent_decode(char  *esc,
     char *ptr;
     
     /* This is max */
-    len = strlen(esc)+1;
+    len = strlen(enc)+1;
     if ((str = malloc(len)) == NULL){
 	clicon_err(OE_UNIX, errno, "malloc"); 
 	goto done;
     }
     memset(str, 0, len);
     j = 0;
-    for (i=0; i<strlen(esc); i++){
-	if (esc[i] == '%' && strlen(esc)-i > 2 && 
-	    isxdigit(esc[i+1]) && isxdigit(esc[i+2])){
-	    hstr[0] = esc[i+1];
-	    hstr[1] = esc[i+2];
+    for (i=0; i<strlen(enc); i++){
+	if (enc[i] == '%' && strlen(enc)-i > 2 && 
+	    isxdigit(enc[i+1]) && isxdigit(enc[i+2])){
+	    hstr[0] = enc[i+1];
+	    hstr[1] = enc[i+2];
 	    hstr[2] = 0;
 	    str[j] = strtoul(hstr, &ptr, 16);
 	    i += 2;
 	}
 	else
-	    str[j] = esc[i];
+	    str[j] = enc[i];
 	j++;
     }
     str[j++] = '\0';
@@ -265,8 +293,9 @@ uri_percent_decode(char  *esc,
 }
 
 /*! Escape characters according to XML definition
- * @param[in]   str    Not-encoded input string     
- * @param[out]  escp   Encoded/escaped malloced output string
+ * @param[out]  encp   Encoded malloced output string
+ * @param[in]   fmt    Not-encoded input string (stdarg format string)
+ * @param[in]   ...    stdarg variable parameters
  * @retval      0      OK
  * @retval     -1      Error
  * @see https://www.w3.org/TR/2008/REC-xml-20081126/#syntax chapter 2.6
@@ -274,8 +303,7 @@ uri_percent_decode(char  *esc,
  * @see AMPERSAND mode in clixon_xml_parse.l
  * @code
  *   char *encstr = NULL;
- *   char *val = "a<>b";
- *   if (xml_chardata_encode(str, &encstr) < 0)
+ *   if (xml_chardata_encode(&encstr, "fmtstr<>& %s", "substr<>") < 0)
  *      err;
  *   if (encstr)
  *      free(encstr);
@@ -289,16 +317,34 @@ uri_percent_decode(char  *esc,
  * Optionally >
  */
 int
-xml_chardata_encode(char  *str, 
-		    char **escp)
+xml_chardata_encode(char **escp,
+		    char  *fmt,...)
 {
-    int   retval = -1;
-    char *esc = NULL;
-    int   l;
-    int   len;
-    int   i, j;
-    int   cdata; /* when set, skip encoding */
+    int     retval = -1;
+    char   *str = NULL;  /* Expanded format string w stdarg */
+    int     fmtlen;
+    char   *esc = NULL;
+    int     l;
+    int     len;
+    int     i, j;
+    int     cdata; /* when set, skip encoding */
+    va_list args;
     
+    /* Two steps: (1) read in the complete format string */
+    va_start(args, fmt); /* dryrun */
+    fmtlen = vsnprintf(NULL, 0, fmt, args) + 1;
+    va_end(args);
+    if ((str = malloc(fmtlen)) == NULL){
+	clicon_err(OE_UNIX, errno, "malloc");
+	goto done;
+    }
+    memset(str, 0, fmtlen);
+    va_start(args, fmt); /* real */
+    fmtlen = vsnprintf(str, fmtlen, fmt, args) + 1;
+    va_end(args);
+    /* Now str is the combined fmt + ... */
+
+    /* Step (2) encode and expand str --> enc */
     /* First compute length (do nothing) */
     len = 0; cdata = 0;
     for (i=0; i<strlen(str); i++){
@@ -381,6 +427,8 @@ xml_chardata_encode(char  *str,
     *escp = esc;
     retval = 0;
  done:
+    if (str)
+	free(str);
     if (retval < 0 && esc)
 	free(esc);
     return retval;
diff --git a/lib/src/clixon_xml.c b/lib/src/clixon_xml.c
index 451d6128..9b09d34c 100644
--- a/lib/src/clixon_xml.c
+++ b/lib/src/clixon_xml.c
@@ -1018,7 +1018,7 @@ clicon_xml2file(FILE  *f,
     case CX_BODY:
 	if ((val = xml_value(x)) == NULL) /* incomplete tree */
 	    break;
-	if (xml_chardata_encode(val, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", val) < 0)
 	    goto done;
 	fprintf(f, "%s", encstr);
 	break;
@@ -1142,7 +1142,7 @@ clicon_xml2cbuf(cbuf  *cb,
     case CX_BODY:
 	if ((val = xml_value(x)) == NULL) /* incomplete tree */
 	    break;
-	if (xml_chardata_encode(val, &encstr) < 0)
+	if (xml_chardata_encode(&encstr, "%s", val) < 0)
 	    goto done;
 	cprintf(cb, "%s", encstr);
 	break;
diff --git a/lib/src/clixon_xml_map.c b/lib/src/clixon_xml_map.c
index ce9716b2..d9c394cf 100644
--- a/lib/src/clixon_xml_map.c
+++ b/lib/src/clixon_xml_map.c
@@ -1006,7 +1006,7 @@ api_path_fmt2api_path(char  *api_path_fmt,
 		    clicon_err(OE_UNIX, errno, "cv2str_dup");
 		    goto done;
 		}
-		if (uri_percent_encode(str, &strenc) < 0)
+		if (uri_percent_encode(&strenc, "%s", str) < 0)
 		    goto done;
 		cprintf(cb, "%s", strenc); 
 		free(strenc); strenc = NULL;
diff --git a/lib/src/clixon_yang_module.c b/lib/src/clixon_yang_module.c
index 4acf1f34..76f0b5f1 100644
--- a/lib/src/clixon_yang_module.c
+++ b/lib/src/clixon_yang_module.c
@@ -153,6 +153,7 @@ x            +--ro namespace           inet:uri
                +--ro name        yang:yang-identifier
                +--ro revision    union
                +--ro schema?     inet:uri
+ * @see netconf_create_hello
  */
 int
 yang_modules_state_get(clicon_handle    h,
diff --git a/test/lib.sh b/test/lib.sh
index a5d0da09..4404bbee 100755
--- a/test/lib.sh
+++ b/test/lib.sh
@@ -130,9 +130,10 @@ expecteof(){
 ret=$($cmd<<EOF 
 $input
 EOF
-) 
-  if [ $? -ne $retval ]; then
-      echo -e "\e[31m\nError in Test$testnr [$testname]:"
+)
+  r=$? 
+  if [ $r -ne $retval ]; then
+      echo -e "\e[31m\nError ($r != $retval) in Test$testnr [$testname]:"
       echo -e "\e[0m:"
       exit -1
   fi
@@ -141,7 +142,7 @@ EOF
   if [ -z "$ret" -a -z "$expect" ]; then
       return
   fi
-  match=`echo "$ret" | grep -Eo "$expect"`
+  match=`echo "$ret" | grep -GZo "$expect"`
 #  echo "ret:\"$ret\""
 #  echo "expect:\"$expect\""
 #  echo "match:\"$match\""
diff --git a/test/test_feature.sh b/test/test_feature.sh
index 892c3dbc..e49929d2 100755
--- a/test/test_feature.sh
+++ b/test/test_feature.sh
@@ -91,10 +91,11 @@ new "netconf validate enabled feature"
 expecteof "$clixon_netconf -qf $cfg -y $fyang" 0 "<rpc><validate><source><candidate/></source></validate></rpc>]]>]]>" "^<rpc-reply><ok/></rpc-reply>]]>]]>$"
 
 new "netconf disabled feature"
-expecteof "$clixon_netconf -qf $cfg -y $fyang" 0 "<rpc><edit-config><target><candidate/></target><config><A>foo</A></config></edit-config></rpc>]]>]]>" '^<rpc-reply><rpc-error><error-tag>operation-failed</error-tag><error-type>protocol</error-type><error-severity>error</error-severity><error-message>XML node config/A has no corresponding yang specification \(Invalid XML or wrong Yang spec?'
+expecteof "$clixon_netconf -qf $cfg -y $fyang" 0 "<rpc><edit-config><target><candidate/></target><config><A>foo</A></config></edit-config></rpc>]]>]]>" '^<rpc-reply><rpc-error><error-tag>operation-failed</error-tag><error-type>protocol</error-type><error-severity>error</error-severity><error-message>XML node config/A has no corresponding yang specification (Invalid XML or wrong Yang spec?'
 
+# This is difficult test since changes to the module list are frequent
 new "netconf schema resource, RFC 7895"
-expecteof "$clixon_netconf -qf $cfg -y $fyang" 0 '<rpc><get><filter type="xpath" select="modules-state/module" xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library"/></get></rpc>]]>]]>' '^<rpc-reply><data><modules-state><module><name>example</name><revision/><namespace/><feature>A</feature></module><module><name>ietf-inet-types</name><revision>2013-07-15</revision><namespace>urn:ietf:params:xml:ns:yang:ietf-inet-types</namespace></module><module><name>ietf-interfaces</name><revision>2014-05-08</revision><namespace>urn:ietf:params:xml:ns:yang:ietf-interfaces</namespace></module><module><name>ietf-routing</name><revision>2014-10-26</revision><namespace>urn:ietf:params:xml:ns:yang:ietf-routing</namespace><feature>router-id</feature></module><module><name>ietf-yang-library</name><revision>2016-06-21</revision><namespace>urn:ietf:params:xml:ns:yang:ietf-yang-library</namespace></module><module><name>ietf-yang-types</name><revision>2013-07-15</revision><namespace>urn:ietf:params:xml:ns:yang:ietf-yang-types</namespace></module></modules-state></data></rpc-reply>]]>]]>$'
+expecteof "$clixon_netconf -qf $cfg -y $fyang" 0 '<rpc><get><filter type="xpath" select="modules-state/module" xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library"/></get></rpc>]]>]]>' '^<rpc-reply><data><modules-state><module><name>example</name><revision/><namespace/><feature>A</feature></module><module><name>ietf-inet-types</name><revision>2013-07-15</revision><namespace>urn:ietf:params:xml:ns:yang:ietf-inet-types</namespace></module><module><name>ietf-interfaces</name><revision>2014-05-08</revision><namespace>urn:ietf:params:xml:ns:yang:ietf-interfaces</namespace></module><module><name>ietf-netconf</name><revision>2011-06-01</revision><namespace>urn:ietf:params:xml:ns:netconf:base:1.0</namespace></module><module><name>ietf-routing</name><revision>2014-10-26</revision><namespace>urn:ietf:params:xml:ns:yang:ietf-routing</namespace><feature>router-id</feature></module><module><name>ietf-yang-library</name><revision>2016-06-21</revision><namespace>urn:ietf:params:xml:ns:yang:ietf-yang-library</namespace></module><module><name>ietf-yang-types</name><revision>2013-07-15</revision><namespace>urn:ietf:params:xml:ns:yang:ietf-yang-types</namespace></module></modules-state></data></rpc-reply>]]>]]>$'
 
 new "Kill backend"
 # kill backend
diff --git a/test/test_netconf.sh b/test/test_netconf.sh
index df5ac83d..68efcbdc 100755
--- a/test/test_netconf.sh
+++ b/test/test_netconf.sh
@@ -98,8 +98,8 @@ if [ $? -ne 0 ]; then
 fi
 
 new "netconf hello"
-expecteof "$clixon_netconf -f $cfg -y $fyang" 0 '<rpc message-id="101"><get-config><source><candidate/></source></get-config></rpc>]]>]]>' '^<hello><capabilities><capability>urn:ietf:params:netconf:capability:yang-library:1.0\?revision="2016-06-21"\&module-set-id=42</capability></capabilities><session-id>'
-exit
+expecteof "$clixon_netconf -f $cfg -y $fyang" 0 '<rpc message-id="101"><get-config><source><candidate/></source></get-config></rpc>]]>]]>' '^<hello xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"><capabilities><capability>urn:ietf:params:netconf:base:1.1</capability><capability>urn:ietf:params:netconf:capability:yang-library:1.0?revision="2016-06-21"&amp; module-set-id=42</capability></capabilities><session-id>[0-9]*</session-id></hello>]]>]]><rpc-reply message-id="101"><data/></rpc-reply>]]>]]>$'
+
 new "netconf get-config"
 expecteof "$clixon_netconf -qf $cfg -y $fyang" 0 '<rpc message-id="101"><get-config><source><candidate/></source></get-config></rpc>]]>]]>' '^<rpc-reply message-id="101"><data/></rpc-reply>]]>]]>$'
 
@@ -112,6 +112,7 @@ expecteof "$clixon_netconf -qf $cfg -y $fyang" 0 '<rpc message-id="101"><get-con
 new "Add subtree eth/0/0 using none and create which should add eth/0/0"
 expecteof "$clixon_netconf -qf $cfg -y $fyang" 0 '<rpc><edit-config><target><candidate/></target><config><interfaces><interface operation="create"><name>eth/0/0</name><type>ex:eth</type></interface></interfaces></config><default-operation>none</default-operation> </edit-config></rpc>]]>]]>' "^<rpc-reply><ok/></rpc-reply>]]>]]>$"
 
+
 # Too many quotes, (single inside double inside single) need to fool bash
 cat <<EOF > $tmp # new
 <rpc><get-config><source><candidate/></source><filter type="xpath" select="/interfaces/interface[name='eth/0/0']"/></get-config></rpc>]]>]]>
@@ -243,9 +244,6 @@ expecteof "$clixon_netconf -qf $cfg -y $fyang" 0 "<rpc><ex:empty/></rpc>]]>]]>"
 new "netconf client-side rpc"
 expecteof "$clixon_netconf -qf $cfg -y $fyang" 0 "<rpc><ex:client-rpc><request>example</request></ex:client-rpc></rpc>]]>]]>" "^<rpc-reply><result>ok</result></rpc-reply>]]>]]>$"
 
-new "netconf subscription"
-expectwait "$clixon_netconf -qf $cfg -y $fyang" "<rpc><create-subscription><stream>NETCONF</stream></create-subscription></rpc>]]>]]>" '^<rpc-reply><ok/></rpc-reply>]]>]]><notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"><eventTime>201' 10
-
 new "Kill backend"
 # kill backend
 sudo clixon_backend -zf $cfg