perf stat: Clear screen only if output file is a tty

The --interval-clear option makes perf stat to clear the terminal at
each interval.  But it doesn't need to clear the screen when it saves
to a file.  Make it fail when it's enabled with the output options.

  $ perf stat -I 1 --interval-clear -o myfile true
  --interval-clear does not work with output

   Usage: perf stat [<options>] [<command>]

      -o, --output <file>   output file name
          --log-fd <n>      log output to fd, instead of stderr
          --interval-clear  clear screen in between new interval

Signed-off-by: Namhyung Kim <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Athira Jajeev <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Xing Zhengjun <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 8 insertions, 0 deletions

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index d5e1670bca20..1d79801f4e84 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -2403,6 +2403,14 @@ int cmd_stat(int argc, const char **argv)
 		}
 	}
 
+	if (stat_config.interval_clear && !isatty(fileno(output))) {
+		fprintf(stderr, "--interval-clear does not work with output\n");
+		parse_options_usage(stat_usage, stat_options, "o", 1);
+		parse_options_usage(NULL, stat_options, "log-fd", 0);
+		parse_options_usage(NULL, stat_options, "interval-clear", 0);
+		return -1;
+	}
+
 	stat_config.output = output;
 
 	/*