diff --git a/degesch.c b/degesch.c
index ecc15d8..8d37622 100644
--- a/degesch.c
+++ b/degesch.c
@@ -3647,6 +3647,39 @@ config_dump (struct config_item_ *root, struct str_vector *output)
 	config_dump_item (root, &data);
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+static int
+str_vector_sort_cb (const void *a, const void *b)
+{
+	return strcmp (*(const char **) a, *(const char **) b);
+}
+
+static void
+str_vector_sort (struct str_vector *self)
+{
+	qsort (self->vector, self->len, sizeof *self->vector, str_vector_sort_cb);
+}
+
+static void
+dump_matching_options
+	(struct app_context *ctx, const char *mask, struct str_vector *output)
+{
+	config_dump (ctx->config.root, output);
+	str_vector_sort (output);
+
+	// Filter out results by wildcard matching
+	for (size_t i = 0; i < output->len; i++)
+	{
+		// Yeah, I know
+		const char *line = output->vector[i];
+		char *key = xstrndup (line, strcspn (line, " "));
+		if (fnmatch (mask, key, 0))
+			str_vector_remove (output, i--);
+		free (key);
+	}
+}
+
 // --- User input handling -----------------------------------------------------
 
 static bool handle_command_help (struct app_context *, char *);
@@ -3773,6 +3806,78 @@ handle_command_buffer (struct app_context *ctx, char *arguments)
 	return true;
 }
 
+static ssize_t
+str_vector_find (const struct str_vector *v, const char *s)
+{
+	for (size_t i = 0; i < v->len; i++)
+		if (!strcmp (v->vector[i], s))
+			return i;
+	return -1;
+}
+
+static bool
+replace_string_array
+	(struct config_item_ *item, struct str_vector *array, struct error **e)
+{
+	char *changed = join_str_vector (array, ',');
+	struct str tmp = { .str = changed, .len = strlen (changed) };
+	bool result = config_item_set_from (item,
+		config_item_string_array (&tmp), e);
+	free (changed);
+	return result;
+}
+
+static bool
+handle_command_set_add
+	(struct config_item_ *item, const char *value, struct error **e)
+{
+	bool result = false;
+	struct str_vector items;
+	str_vector_init (&items);
+	split_str (item->value.string.str, ',', &items);
+
+	if (str_vector_find (&items, value) != -1)
+		error_set (e, "already present in the array: %s", value);
+	else
+	{
+		str_vector_add (&items, value);
+		result = replace_string_array (item, &items, e);
+	}
+
+	str_vector_free (&items);
+	return result;
+}
+
+static bool
+handle_command_set_remove
+	(struct config_item_ *item, const char *value, struct error **e)
+{
+	bool result = false;
+	struct str_vector items;
+	str_vector_init (&items);
+	split_str (item->value.string.str, ',', &items);
+
+	ssize_t i = str_vector_find (&items, value);
+	if (i == -1)
+		error_set (e, "not present in the array: %s", value);
+	else
+	{
+		str_vector_remove (&items, i);
+		result = replace_string_array (item, &items, e);
+	}
+
+	str_vector_free (&items);
+	return result;
+}
+
+static bool
+handle_command_set_replace (struct app_context *ctx,
+	struct config_item_ *item, struct config_item_ *new_, struct error **e)
+{
+	// TODO: replace the item (or log error)
+	return false;
+}
+
 static bool
 handle_command_set_assign
 	(struct app_context *ctx, struct str_vector *all, char *arguments)
@@ -3815,53 +3920,48 @@ handle_command_set_assign
 			config_item_get (ctx->config.root, key, NULL);
 		hard_assert (item);
 
+		struct error *e = NULL;
 		if ((add | remove) && item->type != CONFIG_ITEM_STRING_ARRAY)
-			buffer_send_error (ctx, ctx->global_buffer,
-				"Option is not a string array: %s", key);
+			// FIXME: it can also be null, which makes this message confusing
+			error_set (&e, "not a string array");
 		else if (add)
-			; // TODO: add to string array (or log error)
+			handle_command_set_add (item, new_->value.string.str, &e);
 		else if (remove)
-			; // TODO: remove from string array (or log error)
+			handle_command_set_remove (item, new_->value.string.str, &e);
 		else
-			; // TODO: reset the value
+			handle_command_set_replace (ctx, item, new_, &e);
+
+		if (e)
+		{
+			buffer_send_error (ctx, ctx->global_buffer,
+				"Failed to set option \"%s\": %s", key, e->message);
+			error_free (e);
+		}
+		else
+		{
+			struct str_vector tmp;
+			str_vector_init (&tmp);
+			dump_matching_options (ctx, key, &tmp);
+			buffer_send_status (ctx, ctx->global_buffer,
+				"Option changed: %s", tmp.vector[0]);
+			str_vector_free (&tmp);
+		}
 		free (key);
 	}
 	config_item_destroy (new_);
 	return true;
 }
 
-static int
-str_vector_sort_cb (const void *a, const void *b)
-{
-	return strcmp (*(const char **) a, *(const char **) b);
-}
-
-static void
-str_vector_sort (struct str_vector *self)
-{
-	qsort (self->vector, self->len, sizeof *self->vector, str_vector_sort_cb);
-}
-
 static bool
 handle_command_set (struct app_context *ctx, char *arguments)
 {
-	struct str_vector all;
-	str_vector_init (&all);
-	config_dump (ctx->config.root, &all);
-	str_vector_sort (&all);
-
 	char *option = "*";
 	if (*arguments)
 		option = cut_word (&arguments);
 
-	// Filter out results by wildcard matching
-	for (size_t i = 0; i < all.len; i++)
-	{
-		char *key = xstrndup (all.vector[i], strcspn (all.vector[i], " "));
-		if (fnmatch (option, key, 0))
-			str_vector_remove (&all, i--);
-		free (key);
-	}
+	struct str_vector all;
+	str_vector_init (&all);
+	dump_matching_options (ctx, option, &all);
 
 	bool result = true;
 	if (!all.len)