[PATCH 5.4 096/320] bpftool: Enable line buffering for stdout

[Greg Kroah-Hartman]

From: Paul Chaignon <paul@xxxxxxxxxxxxx>

[ Upstream commit 1a1a0b0364ad291bd8e509da104ac8b5b1afec5d ]

The output of bpftool prog tracelog is currently buffered, which is
inconvenient when piping the output into other commands. A simple
tracelog | grep will typically not display anything. This patch fixes it
by enabling line buffering on stdout for the whole bpftool binary.

Fixes: 30da46b5dc3a ("tools: bpftool: add a command to dump the trace pipe")
Signed-off-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
Signed-off-by: Paul Chaignon <paul@xxxxxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Acked-by: Yonghong Song <yhs@xxxxxx>
Link: https://lore.kernel.org/bpf/20211220214528.GA11706@Mem
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 tools/bpf/bpftool/main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 7d3cfb0ccbe61..4b03983acbefe 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -362,6 +362,8 @@ int main(int argc, char **argv)
 	};
 	int opt, ret;
 
+	setlinebuf(stdout);
+
 	last_do_help = do_help;
 	pretty_output = false;
 	json_output = false;
-- 
2.34.1