bpftool: Enable line buffering for stdout

[ 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@isovalent.com>
Signed-off-by: Paul Chaignon <paul@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211220214528.GA11706@Mem
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 02eaaf0..d27ec4f 100644 (file)
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -402,6 +402,8 @@ int main(int argc, char **argv)
        };
        int opt, ret;
 
+       setlinebuf(stdout);
+
        last_do_help = do_help;
        pretty_output = false;
        json_output = false;