diff --git a/common/sort-utils.c b/common/sort-utils.c
index d5b15a1a..bae2cd16 100644
--- a/common/sort-utils.c
+++ b/common/sort-utils.c
@@ -16,7 +16,9 @@
 
 #include <strings.h>
 #include <string.h>
+#include <ctype.h>
 #include "common/sort-utils.h"
+#include "common/messages.h"
 
 int compare_init(struct compare *comp, const struct sortdef *sortdef)
 {
@@ -55,3 +57,157 @@ int compare_add_sort_key(struct compare *comp, const char *key)
 	}
 	return 0;
 }
+
+/*
+ * Append given sort by its @id from associated sortdef.
+ *
+ * Return: 0  if id is valid
+ *         -1 if id not in sortdef
+ */
+int compare_add_sort_id(struct compare *comp, int id)
+{
+	int i;
+
+	if (!comp->sortdef)
+		return -1;
+
+	if (id < 0)
+		return -1;
+
+	for (i = 0; i < SORT_MAX_KEYS; i++) {
+		if (comp->sortdef[i].name == NULL)
+			return -1;
+		if (comp->sortdef[i].id == id) {
+			comp->comp[comp->count] = comp->sortdef[i].comp;
+			comp->count++;
+			break;
+		}
+	}
+	return 0;
+}
+
+/*
+ * Consume word-like list of key names (coma separated) and return its id if
+ * found in sortdef. The @next pointer is advanced to the next expected key start.
+ * Empty and NULL @next is accepted.
+ *
+ * Key lookup is case insensitive.
+ *
+ * Retrun: id from sortdef if a matching
+ *         -1 on error
+ *         -2 end of buffer
+ */
+int compare_parse_key_to_id(const struct compare *comp, const char **next)
+{
+	const char *tmp = *next, *start = *next;
+
+	if (!comp->sortdef)
+		return -1;
+
+	/* No sort string (use defaults), or last. */
+	if (!*next || !**next)
+		return -2;
+
+	do {
+		/* End of word. */
+		if (*tmp == ',' || *tmp == 0) {
+			/* Look up in sortdef. */
+			for (int i = 0; comp->sortdef[i].name; i++) {
+				int len = strlen(comp->sortdef[i].name);
+
+				if (strncasecmp(start, comp->sortdef[i].name, len) == 0) {
+					/* Point to last NUL. */
+					*next = tmp;
+					/* Or the next valid char. */
+					if (*tmp)
+						(*next)++;
+					return comp->sortdef[i].id;
+				}
+			}
+			/* Not found, report which one. */
+			*next = start;
+			return -1;
+		}
+		/* Invalid char found. */
+		if (!isalnum(*tmp)) {
+			*next = tmp;
+			return -1;
+		}
+		tmp++;
+	} while(1);
+
+	/* Not found. */
+	*next = start;
+	return -1;
+}
+
+/* Read id of its associated sort @key.  Key lookup is case insensitive. */
+int compare_key_id(const struct compare *comp, const char *key)
+{
+	if (!comp->sortdef)
+		return -1;
+
+	for (int i = 0; comp->sortdef[i].name; i++)
+		if (strcasecmp(comp->sortdef[i].name, key) == 0)
+			return comp->sortdef[i].id;
+	return -1;
+}
+
+/* Read sort key name associated to @id. */
+const char *compare_id_name(const struct compare *comp, int id)
+{
+	if (!comp->sortdef)
+		return NULL;
+
+	for (int i = 0; comp->sortdef[i].name; i++)
+		if (comp->sortdef[i].id == id)
+			return comp->sortdef[i].name;
+	return NULL;
+}
+
+/*
+ * Check if the given @id (must exist in the associated sortdef) enabled in
+ * @comp.
+ */
+bool compare_has_id(const struct compare *comp, int id)
+{
+	int idx;
+
+	if (!comp->sortdef)
+		return false;
+
+	idx = -1;
+	for (int i = 0; comp->sortdef[i].name; i++)
+		if (comp->sortdef[i].id == id)
+			idx = i;
+
+	if (idx < 0)
+		return false;
+
+	for (int i = 0; i < comp->count; i++)
+		if (comp->comp[i] == comp->sortdef[idx].comp)
+			return true;
+	return false;
+}
+
+/*
+ * Set up compare structure with associated sortdef from a user specified list
+ * of keys.
+ */
+int compare_setup_sort(struct compare *comp, const struct sortdef *sdef, const char *def)
+{
+	const char *tmp;
+	int id;
+
+	tmp = def;
+	do {
+		id = compare_parse_key_to_id(comp, &tmp);
+		if (id == -1) {
+			error("unknown sort key: %s", tmp);
+			return -1;
+		}
+		compare_add_sort_id(comp, id);
+	} while (id >= 0);
+
+	return 0;
+}
diff --git a/common/sort-utils.h b/common/sort-utils.h
index e2a355b3..b92a8e72 100644
--- a/common/sort-utils.h
+++ b/common/sort-utils.h
@@ -17,6 +17,8 @@
 #ifndef __COMMON_SORT_UTILS_H__
 #define __COMMON_SORT_UTILS_H__
 
+#include <stdbool.h>
+
 /*
  * Example:
 
@@ -48,7 +50,7 @@ void test() {
 		  .desc = "sort by id" },
 		{ .name = "size", .comp = (sort_cmp_t)cmp_entry_size,
 		  .desc = "sort by entry size" },
-		{ .name = NULL,   .comp = NULL }
+		SORTDEF_END
 	};
 	// List of keys to use for sort (e.g. from command line options)
 	const char *sortby[] = { "size", "id" };
@@ -66,6 +68,9 @@ void test() {
 }
  */
 
+#define SORTDEF_END		{ .name = NULL, .comp = NULL }
+#define SORT_MAX_KEYS		32
+
 typedef int (*sort_cmp_t)(const void *a, const void *b);
 typedef int (*sort_r_cmp_t)(const void *a, const void *b, void *data);
 
@@ -73,10 +78,12 @@ struct sortdef {
 	const char *name;
 	const char *desc;
 	sort_cmp_t comp;
+	/* User defined identifier of this sort key. */
+	int id;
 };
 
 struct compare {
-	sort_cmp_t comp[32];
+	sort_cmp_t comp[SORT_MAX_KEYS];
 	unsigned long invert_map;
 	int count;
 	const struct sortdef *sortdef;
@@ -85,5 +92,11 @@ struct compare {
 int compare_init(struct compare *comp, const struct sortdef *sortdef);
 int compare_cmp_multi(const void *a, const void *b, const struct compare *comp);
 int compare_add_sort_key(struct compare *comp, const char *key);
+int compare_parse_key_to_id(const struct compare *comp, const char **next);
+int compare_add_sort_id(struct compare *comp, int id);
+int compare_key_id(const struct compare *comp, const char *key);
+const char *compare_id_name(const struct compare *comp, int id);
+bool compare_has_id(const struct compare *comp, int id);
+int compare_setup_sort(struct compare *comp, const struct sortdef *sdef, const char *def);
 
 #endif