[PATCH 6/6] perf tools: Enhancement for perf list for unexpected input.

[Dongsheng Yang]

Example:
	# perf list test

	List of pre-defined events (to be used in -e):
	# echo $?
	0

Verification:
	# perf list test

	Error: No event for test.
	Usage:
		perf list [hw|sw|cache|tracepoint|pmu|event_glob]
	# echo $?
	255

Signed-off-by: Dongsheng Yang <yangds.fnst@xxxxxxxxxxxxxx>
---
 tools/perf/builtin-list.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-list.c b/tools/perf/builtin-list.c
index 82d54b6..ba23f65 100644
--- a/tools/perf/builtin-list.c
+++ b/tools/perf/builtin-list.c
@@ -63,9 +63,11 @@ int cmd_list(int argc, const char **argv, const char *prefix __maybe_unused)
 		else {
 			char *sep = strchr(argv[i], ':'), *s;
 			int sep_idx;
+			unsigned int count;
 
 			if (sep == NULL) {
-				print_events(argv[i], false);
+				if(!(count = print_events(argv[i], false)))
+					goto err_out;
 				continue;
 			}
 			sep_idx = sep - argv[i];
@@ -74,9 +76,16 @@ int cmd_list(int argc, const char **argv, const char *prefix __maybe_unused)
 				return -1;
 
 			s[sep_idx] = '\0';
-			print_tracepoint_events(s, s + sep_idx + 1, false);
+			if (!(count = print_tracepoint_events(s, s + sep_idx + 1, false)))
+				goto err_out;
 			free(s);
 		}
 	}
+
 	return 0;
+
+err_out:
+	printf("\nError: No event for %s.\n", argv[i]);
+	printf("Usage:\n\t%s\n", list_usage[0]);
+	return -1;
 }
-- 
1.8.2.1

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