perf list: Remove blank lines, headers when piping output

So that one can, for instance, use it with wc -l:

  # perf list *:*write* | wc -l
  60

Or to look for the "bio" tracepoints, without 'perf list' headers:

  # perf list *:*bio* | head
    block:block_bio_backmerge                          [Tracepoint event]
    block:block_bio_bounce                             [Tracepoint event]
    block:block_bio_complete                           [Tracepoint event]
    block:block_bio_frontmerge                         [Tracepoint event]
    block:block_bio_queue                              [Tracepoint event]
    block:block_bio_remap                              [Tracepoint event]
  #

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-ts7sc0x8u4io4cifzkup4j44@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/tools/perf/builtin-list.c b/tools/perf/builtin-list.c
index af5bd0514108..602414040344 100644
--- a/tools/perf/builtin-list.c
+++ b/tools/perf/builtin-list.c
@@ -36,7 +36,7 @@ int cmd_list(int argc, const char **argv, const char *prefix __maybe_unused)
 
 	setup_pager();
 
-	if (!raw_dump)
+	if (!raw_dump && pager_in_use())
 		printf("\nList of pre-defined events (to be used in -e):\n\n");
 
 	if (argc == 0) {