diff --git a/nmsg/msgmod/message.c b/nmsg/msgmod/message.c
index bac05129..777bb6d1 100644
--- a/nmsg/msgmod/message.c
+++ b/nmsg/msgmod/message.c
@@ -491,12 +491,12 @@ nmsg_message_to_pres(struct nmsg_message *msg, char **pres, const char *endline)
 }
 
 nmsg_res
-_nmsg_message_to_json(nmsg_message_t msg, struct nmsg_strbuf *sb) {
+_nmsg_message_to_json(nmsg_output_t output, nmsg_message_t msg, struct nmsg_strbuf *sb) {
 	if (msg->mod == NULL)
 		return (nmsg_res_failure);
 	switch (msg->mod->plugin->type) {
 	case nmsg_msgmod_type_transparent:
-		return (_nmsg_message_payload_to_json(msg, sb));
+		return (_nmsg_message_payload_to_json(output, msg, sb));
 	case nmsg_msgmod_type_opaque:
 		return (nmsg_res_notimpl);
 	default:
@@ -510,7 +510,7 @@ nmsg_message_to_json(nmsg_message_t msg, char **json) {
 	struct nmsg_strbuf_storage sbs;
 	struct nmsg_strbuf *sb = _nmsg_strbuf_init(&sbs);
 
-	res = _nmsg_message_to_json(msg, sb);
+	res = _nmsg_message_to_json(NULL, msg, sb);
 	if (res == nmsg_res_success) {
 		*json = _nmsg_strbuf_detach(sb);
 	}
diff --git a/nmsg/msgmod/transparent.h b/nmsg/msgmod/transparent.h
index 4bb60636..2efb0715 100644
--- a/nmsg/msgmod/transparent.h
+++ b/nmsg/msgmod/transparent.h
@@ -65,7 +65,7 @@ _nmsg_msgmod_pres_to_payload_finalize(struct nmsg_msgmod *mod, void *cl,
 				      uint8_t **pbuf, size_t *sz);
 
 nmsg_res
-_nmsg_message_payload_to_json(struct nmsg_message *msg, struct nmsg_strbuf *sb);
+_nmsg_message_payload_to_json(nmsg_output_t output, struct nmsg_message *msg, struct nmsg_strbuf *sb);
 
 nmsg_res
 _nmsg_message_payload_to_json_load(struct nmsg_message *msg,
diff --git a/nmsg/msgmod/transparent_payload.c b/nmsg/msgmod/transparent_payload.c
index 55ffd78d..6d0197db 100644
--- a/nmsg/msgmod/transparent_payload.c
+++ b/nmsg/msgmod/transparent_payload.c
@@ -276,7 +276,7 @@ _nmsg_message_payload_to_pres_load(struct nmsg_message *msg,
 }
 
 nmsg_res
-_nmsg_message_payload_to_json(struct nmsg_message *msg, struct nmsg_strbuf *sb) {
+_nmsg_message_payload_to_json(nmsg_output_t output, struct nmsg_message *msg, struct nmsg_strbuf *sb) {
 	Nmsg__NmsgPayload *np;
 	ProtobufCMessage *m;
 	nmsg_res res;
@@ -285,6 +285,7 @@ _nmsg_message_payload_to_json(struct nmsg_message *msg, struct nmsg_strbuf *sb)
 
 	struct nmsg_msgmod_field *field;
 	const char *vname, *mname;
+	uint32_t oper_val = 0, group_val = 0, source_val = 0;
 
 	struct tm tm;
 	time_t t;
@@ -329,29 +330,46 @@ _nmsg_message_payload_to_json(struct nmsg_message *msg, struct nmsg_strbuf *sb)
 	declare_json_value(sb, "mname", false);
 	append_json_value_string(sb, mname, strlen(mname));
 
-	if (np->has_source) {
-		sb_tmp_len = snprintf(sb_tmp, sizeof(sb_tmp), "%08x", np->source);
+	if (output != NULL && output->json->source != 0)
+		source_val = output->json->source;
+	else if (np->has_source)
+		source_val = np->source;
+
+	if (source_val != 0) {
+		sb_tmp_len = snprintf(sb_tmp, sizeof(sb_tmp), "%08x", source_val);
 		declare_json_value(sb, "source", false);
 		append_json_value_string(sb, sb_tmp, sb_tmp_len);
 	}
 
-	if (np->has_operator_) {
-		const char *operator = nmsg_alias_by_key(nmsg_alias_operator, np->operator_);
+	if (output != NULL && output->json->operator != 0)
+		oper_val = output->json->operator;
+	else if (np->has_operator_)
+		oper_val = np->operator_;
+
+	if (oper_val != 0) {
+		const char *operator = nmsg_alias_by_key(nmsg_alias_operator, oper_val);
 		declare_json_value(sb, "operator", false);
-		if (operator != NULL) {
+
+		if (operator != NULL)
 			append_json_value_string(sb, operator, strlen(operator));
-		} else {
-			append_json_value_int(sb, np->operator_);
-		}
+		else
+			append_json_value_int(sb, oper_val);
 	}
 
-	if (np->has_group) {
-		const char *group = nmsg_alias_by_key(nmsg_alias_group, np->group);
+	if (output != NULL && output->json->group != 0)
+		group_val = output->json->group;
+	else if (np->has_group)
+		group_val = np->group;
+
+	if (group_val != 0) {
+		const char *group = nmsg_alias_by_key(nmsg_alias_group, group_val);
 		declare_json_value(sb, "group", false);
+
 		if (group != NULL)
 			append_json_value_string(sb, group, strlen(group));
 		else
-			append_json_value_int(sb, np->group);
+			append_json_value_int(sb, group_val);
+
 	}
 
 	declare_json_value(sb, "message", false);
diff --git a/nmsg/output.c b/nmsg/output.c
index 76b696a2..fd93f053 100644
--- a/nmsg/output.c
+++ b/nmsg/output.c
@@ -291,20 +291,53 @@ nmsg_output_set_endline(nmsg_output_t output, const char *endline) {
 
 void
 nmsg_output_set_source(nmsg_output_t output, unsigned source) {
-	if (output->type == nmsg_output_type_stream)
+	switch(output->type) {
+	case nmsg_output_type_stream:
 		output->stream->source = source;
+		break;
+	case nmsg_output_type_pres:
+		output->pres->source = source;
+		break;
+	case nmsg_output_type_json:
+		output->json->source = source;
+		break;
+	default:
+		break;
+	}
 }
 
 void
 nmsg_output_set_operator(nmsg_output_t output, unsigned operator) {
-	if (output->type == nmsg_output_type_stream)
+	switch(output->type) {
+	case nmsg_output_type_stream:
 		output->stream->operator = operator;
+		break;
+	case nmsg_output_type_pres:
+		output->pres->operator = operator;
+		break;
+	case nmsg_output_type_json:
+		output->json->operator = operator;
+		break;
+	default:
+		break;
+	}
 }
 
 void
 nmsg_output_set_group(nmsg_output_t output, unsigned group) {
-	if (output->type == nmsg_output_type_stream)
+	switch(output->type) {
+	case nmsg_output_type_stream:
 		output->stream->group = group;
+		break;
+	case nmsg_output_type_pres:
+		output->pres->group = group;
+		break;
+	case nmsg_output_type_json:
+		output->json->group = group;
+		break;
+	default:
+		break;
+	}
 }
 
 void
diff --git a/nmsg/output_json.c b/nmsg/output_json.c
index 322c4f19..371fdb22 100644
--- a/nmsg/output_json.c
+++ b/nmsg/output_json.c
@@ -27,7 +27,7 @@ _output_json_write(nmsg_output_t output, nmsg_message_t msg) {
 	struct nmsg_strbuf_storage sbs;
 	struct nmsg_strbuf *sb = _nmsg_strbuf_init(&sbs);
 
-	res = _nmsg_message_to_json(msg, sb);
+	res = _nmsg_message_to_json(output, msg, sb);
 	if (res != nmsg_res_success)
 		goto out;
 
diff --git a/nmsg/output_pres.c b/nmsg/output_pres.c
index f78b30a3..2bf058c2 100644
--- a/nmsg/output_pres.c
+++ b/nmsg/output_pres.c
@@ -23,10 +23,12 @@
 nmsg_res
 _output_pres_write(nmsg_output_t output, nmsg_message_t msg) {
 	Nmsg__NmsgPayload *np;
-	const char *vname = NULL;
-	const char *mname = NULL;
-	char *pres_data;
+	char op_buf[sizeof("4294967295")] = {0}, group_buf[sizeof("4294967295")] = {0};
+	const char *op_str = op_buf, *group_str = group_buf;
+	const char *vname = NULL, *mname = NULL;
 	char when[32];
+	char *pres_data;
+	uint32_t oper_val = 0, group_val = 0, source_val = 0;
 	nmsg_msgmod_t mod;
 	nmsg_res res;
 	struct tm tm;
@@ -52,6 +54,40 @@ _output_pres_write(nmsg_output_t output, nmsg_message_t msg) {
 	}
 	vname = nmsg_msgmod_vid_to_vname(np->vid);
 	mname = nmsg_msgmod_msgtype_to_mname(np->vid, np->msgtype);
+
+	if (output->pres->operator != 0)
+		oper_val = output->pres->operator;
+	else if (np->has_operator_)
+		oper_val = np->operator_;
+
+	if (oper_val != 0) {
+		op_str = nmsg_alias_by_key(nmsg_alias_operator, oper_val);
+
+		if (op_str == NULL) {
+			snprintf(op_buf, sizeof(op_buf), "%"PRIu32, oper_val);
+			op_str = op_buf;
+		}
+	}
+
+	if (output->pres->group != 0)
+		group_val = output->pres->group;
+	else if (np->has_group)
+		group_val = np->group;
+
+	if (group_val != 0) {
+		group_str = nmsg_alias_by_key(nmsg_alias_group, group_val);
+
+		if (group_str == NULL) {
+			snprintf(group_buf, sizeof(group_buf), "%"PRIu32, group_val);
+			group_str = group_buf;
+		}
+	}
+
+	if (output->pres->source != 0)
+		source_val = output->pres->source;
+	else if (np->has_source)
+		source_val = np->source;
+
 	fprintf(output->pres->fp, "[%zu] [%s.%09u] [%d:%d %s %s] "
 		"[%08x] [%s] [%s] %s%s",
 		np->has_payload ? np->payload.len : 0,
@@ -59,16 +95,9 @@ _output_pres_write(nmsg_output_t output, nmsg_message_t msg) {
 		np->vid, np->msgtype,
 		vname ? vname : "(unknown)",
 		mname ? mname : "(unknown)",
-		np->has_source ? np->source : 0,
-
-		np->has_operator_ ?
-			nmsg_alias_by_key(nmsg_alias_operator, np->operator_)
-			: "",
-
-		np->has_group ?
-			nmsg_alias_by_key(nmsg_alias_group, np->group)
-			: "",
-
+		source_val,
+		op_str,
+		group_str,
 		output->pres->endline, pres_data);
 	fputs("\n", output->pres->fp);
 	if (output->pres->flush)
diff --git a/nmsg/private.h b/nmsg/private.h
index a348b5fa..08d4ebe4 100644
--- a/nmsg/private.h
+++ b/nmsg/private.h
@@ -232,6 +232,9 @@ struct nmsg_pres {
 	FILE			*fp;
 	bool			flush;
 	char			*endline;
+	unsigned		source;
+	unsigned		operator;
+	unsigned		group;
 };
 
 /* nmsg_json: used by nmsg_input and nmsg_output */
@@ -242,6 +245,9 @@ struct nmsg_json {
 	FILE			*fp;
 	int			orig_fd;
 	bool			flush;
+	unsigned		source;
+	unsigned		operator;
+	unsigned		group;
 };
 
 /* nmsg_stream_input: used by nmsg_input */
@@ -469,7 +475,7 @@ nmsg_res		_nmsg_message_serialize(struct nmsg_message *msg);
 nmsg_message_t		_nmsg_message_from_payload(Nmsg__NmsgPayload *np);
 nmsg_message_t		_nmsg_message_dup(struct nmsg_message *msg);
 nmsg_res		_nmsg_message_dup_protobuf(const struct nmsg_message *msg, ProtobufCMessage **dst);
-nmsg_res		_nmsg_message_to_json(nmsg_message_t msg, struct nmsg_strbuf *sb);
+nmsg_res		_nmsg_message_to_json(nmsg_output_t output, nmsg_message_t msg, struct nmsg_strbuf *sb);
 
 /* from msgmodset.c */
 
diff --git a/src/nmsgtool.c b/src/nmsgtool.c
index 153890e4..31f58f34 100644
--- a/src/nmsgtool.c
+++ b/src/nmsgtool.c
@@ -384,7 +384,8 @@ usage(const char *msg) {
 	if (msg)
 		fprintf(stderr, "%s: usage error: %s\n", argv_program, msg);
 	nmsg_io_destroy(&ctx.io);
-	exit(argv_usage(args, ARGV_USAGE_DEFAULT));
+	argv_usage(args, ARGV_USAGE_DEFAULT);
+	exit(msg == NULL ? EXIT_SUCCESS : EXIT_FAILURE);
 }
 
 void
diff --git a/src/process_args.c b/src/process_args.c
index 4215f4d5..881b8097 100644
--- a/src/process_args.c
+++ b/src/process_args.c
@@ -23,6 +23,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <ctype.h>
 
 #include "nmsgtool.h"
 
@@ -62,6 +63,22 @@ droproot(nmsgtool_ctx *c, FILE *fp_pidfile) {
 			argv_program, c->username);
 }
 
+/* Convert string to non-zero unsigned 32 bit val, returning zero on failure. */
+static uint32_t
+read_uint32_nz(const char *str)
+{
+	char *t;
+	unsigned long val;
+
+	val = strtoul(str, &t, 0);
+	if (*t != '\0')
+		return 0;
+	else if (val > UINT32_MAX)
+		return 0;
+
+	return (uint32_t)val;
+}
+
 void
 process_args(nmsgtool_ctx *c) {
 	char *t;
@@ -141,17 +158,18 @@ process_args(nmsgtool_ctx *c) {
 
 	/* set source, operator, group */
 	if (c->set_source_str != NULL) {
-		c->set_source = (unsigned) strtoul(c->set_source_str, &t, 0);
-		if (*t != '\0')
+		c->set_source = read_uint32_nz(c->set_source_str);
+		if (c->set_source == 0)
 			usage("invalid source ID");
 		if (c->debug >= 2)
 			fprintf(stderr, "%s: nmsg source set to %#.08x\n",
 				argv_program, c->set_source);
 	}
-
 	if (c->set_operator_str != NULL) {
 		c->set_operator = nmsg_alias_by_value(nmsg_alias_operator,
 						      c->set_operator_str);
+		if (c->set_operator == 0)
+			c->set_operator = read_uint32_nz(c->set_operator_str);
 		if (c->set_operator == 0)
 			usage("unknown operator name");
 		if (c->debug >= 2)
@@ -164,6 +182,8 @@ process_args(nmsgtool_ctx *c) {
 	if (c->set_group_str != NULL) {
 		c->set_group = nmsg_alias_by_value(nmsg_alias_group,
 						   c->set_group_str);
+		if (c->set_group == 0)
+			c->set_group = read_uint32_nz(c->set_group_str);
 		if (c->set_group == 0)
 			usage("unknown group name");
 		if (c->debug >= 2)
@@ -175,8 +195,8 @@ process_args(nmsgtool_ctx *c) {
 
 	/* get source, operator, group */
 	if (c->get_source_str != NULL) {
-		c->get_source = (unsigned) strtoul(c->get_source_str, &t, 0);
-		if (*t != '\0')
+		c->get_source = read_uint32_nz(c->get_source_str);
+		if (c->get_source == 0)
 			usage("invalid filter source ID");
 		if (c->debug >= 2)
 			fprintf(stderr, "%s: nmsg source filter set to "
@@ -187,6 +207,8 @@ process_args(nmsgtool_ctx *c) {
 	if (c->get_operator_str != NULL) {
 		c->get_operator = nmsg_alias_by_value(nmsg_alias_operator,
 						      c->get_operator_str);
+		if (c->get_operator == 0)
+			c->get_operator = read_uint32_nz(c->get_operator_str);
 		if (c->get_operator == 0)
 			usage("unknown filter operator name");
 		if (c->debug >= 2)
@@ -200,6 +222,8 @@ process_args(nmsgtool_ctx *c) {
 	if (c->get_group_str != NULL) {
 		c->get_group = nmsg_alias_by_value(nmsg_alias_group,
 						   c->get_group_str);
+		if (c->get_group == 0)
+			c->get_group = read_uint32_nz(c->get_group_str);
 		if (c->get_group == 0)
 			usage("unknown filter group name");
 		if (c->debug >= 2)