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Subject[RFC v2][PATCH 02/11] perf record: introduce special handling for pipe output
Date
Adds special treatment for stdout - if the user specifies '-o -' to
perf record, the intent is that the event stream be written to stdout
rather than to a disk file.

Also, redirect stdout of forked child to stderr - in pipe mode, stdout
of the forked child interferes with the stdout perf stream, so
redirect it to stderr where it can still be seen but won't be mixed in
with the perf output.

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
---
tools/perf/builtin-record.c | 18 +++++++++++++++---
1 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 2654b61..0723fa1 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -36,6 +36,7 @@ static unsigned int page_size;
static unsigned int mmap_pages = 128;
static int freq = 1000;
static int output;
+static int pipe_output = 0;
static const char *output_name = "perf.data";
static int group = 0;
static unsigned int realtime_prio = 0;
@@ -450,7 +451,9 @@ static int __cmd_record(int argc, const char **argv)
exit(-1);
}

- if (!stat(output_name, &st) && st.st_size) {
+ if (!strcmp(output_name, "-"))
+ pipe_output = 1;
+ else if (!stat(output_name, &st) && st.st_size) {
if (!force) {
if (!append_file) {
pr_err("Error, output file %s exists, use -A "
@@ -475,7 +478,10 @@ static int __cmd_record(int argc, const char **argv)
else
flags |= O_TRUNC;

- output = open(output_name, flags, S_IRUSR|S_IWUSR);
+ if (pipe_output)
+ output = STDOUT_FILENO;
+ else
+ output = open(output_name, flags, S_IRUSR | S_IWUSR);
if (output < 0) {
perror("failed to create output file");
exit(-1);
@@ -514,6 +520,8 @@ static int __cmd_record(int argc, const char **argv)
}

if (!child_pid) {
+ if (pipe_output)
+ dup2(2, 1);
close(child_ready_pipe[0]);
close(go_pipe[1]);
fcntl(go_pipe[0], F_SETFD, FD_CLOEXEC);
@@ -565,7 +573,11 @@ static int __cmd_record(int argc, const char **argv)
open_counters(cpumap[i]);
}

- if (file_new) {
+ if (pipe_output) {
+ err = perf_header__write_pipe(output);
+ if (err < 0)
+ return err;
+ } else if (file_new) {
err = perf_header__write(&session->header, output, false);
if (err < 0)
return err;
--
1.6.4.GIT


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