[tip:perf/urgent] perf script: Show proper message when failed list scripts

[tip-bot for He Kuang <tipbot@zytor.com>]

Commit-ID:  88ded4d8d94a550624e1827478e13fecf97a7b0a
Gitweb:     http://git.kernel.org/tip/88ded4d8d94a550624e1827478e13fecf97a7b0a
Author:     He Kuang <hekuang@huawei.com>
AuthorDate: Thu, 4 Aug 2016 11:25:42 +0000
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 15 Aug 2016 13:17:10 -0300

perf script: Show proper message when failed list scripts

Perf shows the usage message when perf scripts folder failed to open,
which misleads users to let them think the command is being mistyped.

This patch shows a proper message and guides users to check the
PERF_EXEC_PATH environment variable in that case.

Before:

  $ perf script --list

  Usage: perf script [<options>]
   or: perf script [<options>] record <script> [<record-options>] <command>
   or: perf script [<options>] report <script> [script-args]
   or: perf script [<options>] <script> [<record-options>] <command>
   or: perf script [<options>] <top-script> [script-args]

      -l, --list            list available scripts

After:

  $ perf script --list
  open(/home/user/perf-core/scripts) failed.
  Check for "PERF_EXEC_PATH" env to set scripts dir.

Signed-off-by: He Kuang <hekuang@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1470309943-153909-1-git-send-email-hekuang@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/builtin-script.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index 9c640a8..45c51eb 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -1690,8 +1690,13 @@ static int list_available_scripts(const struct option *opt __maybe_unused,
 	snprintf(scripts_path, MAXPATHLEN, "%s/scripts", get_argv_exec_path());
 
 	scripts_dir = opendir(scripts_path);
-	if (!scripts_dir)
-		return -1;
+	if (!scripts_dir) {
+		fprintf(stdout,
+			"open(%s) failed.\n"
+			"Check \"PERF_EXEC_PATH\" env to set scripts dir.\n",
+			scripts_path);
+		exit(-1);
+	}
 
 	for_each_lang(scripts_path, scripts_dir, lang_dirent) {
 		snprintf(lang_path, MAXPATHLEN, "%s/%s/bin", scripts_path,