perf record: Fix the -A UI for empty or non-existent perf.data

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>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 90c98082af106da85261a8995224386fcd228c4d..0345aad8eba50c35422062f4337c51f234d66b7a 100644 (file)
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -525,10 +525,14 @@ 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;