[PATCH 2/2] perf-record: improve -A UI for empty or non-existent perf.data

[Pierre Habouzit <pierre.habouzit@intersec.com>]

From: Pierre Habouzit <madcoder@debian.org>

1. Ignore the -A argument if there is no perf.data file
2. Treat an empty file like a non existent file.

Else, perf will try to read the perf.data header, and fail with an error.

Treating an empty file like a non-existent file makes sense, since an
interupted (as in SIGKILLed) perf could leave such files around, and you
don't want to annoy the user with errors for files with no data in it.

Signed-off-by: Pierre Habouzit <pierre.habouzit@intersec.com>
---
 tools/perf/builtin-record.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 6da0992..afbfb9d 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -524,10 +524,14 @@ static int __cmd_record(int argc, const char **argv)
 	signal(SIGCHLD, sig_handler);
 	signal(SIGINT, sig_handler);
 
-	if (!stat(output_name, &st) && !force && !append_file) {
-		fprintf(stderr, "Error, output file %s exists, use -A to append or -f to overwrite.\n",
-				output_name);
-		exit(-1);
+	if (!stat(output_name, &st) && st.st_size) {
+		if (!force && !append_file) {
+			fprintf(stderr, "Error, output file %s exists, use -A to append or -f to overwrite.\n",
+					output_name);
+			exit(-1);
+		}
+	} else {
+		append_file = 0;
 	}
 
 	flags = O_CREAT|O_RDWR;
-- 
1.6.4.rc2.183.g9085a