[PATCH 3/4] perf tools: Setup pager when printing usage and help

[Namhyung Kim <namhyung@kernel.org>]

It's annoying to see error or help message when command has many options
like in perf record, report or top.  So setup pager when print parser
error or help message - it should be OK since no UI is enabled at the
parsing time.  The usage_with_options() already disables it by calling
exit_browser() anyway.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/util/parse-options.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/parse-options.c b/tools/perf/util/parse-options.c
index b8d98229a8af..eeeed98eb26d 100644
--- a/tools/perf/util/parse-options.c
+++ b/tools/perf/util/parse-options.c
@@ -7,6 +7,8 @@
 #define OPT_SHORT 1
 #define OPT_UNSET 2
 
+static struct strbuf error_buf = STRBUF_INIT;
+
 static int opterror(const struct option *opt, const char *reason, int flags)
 {
 	if (flags & OPT_SHORT)
@@ -540,9 +542,11 @@ int parse_options_subcommand(int argc, const char **argv, const struct option *o
 		exit(130);
 	default: /* PARSE_OPT_UNKNOWN */
 		if (ctx.argv[0][1] == '-') {
-			error("unknown option `%s'", ctx.argv[0] + 2);
+			strbuf_addf(&error_buf, "unknown option `%s'",
+				    ctx.argv[0] + 2);
 		} else {
-			error("unknown switch `%c'", *ctx.opt);
+			strbuf_addf(&error_buf, "unknown switch `%c'",
+				    *ctx.opt);
 		}
 		usage_with_options(usagestr, options);
 	}
@@ -711,6 +715,13 @@ int usage_with_options_internal(const char * const *usagestr,
 	if (!usagestr)
 		return PARSE_OPT_HELP;
 
+	setup_pager();
+
+	if (strbuf_avail(&error_buf)) {
+		fprintf(stderr, "  Error: %s\n", error_buf.buf);
+		strbuf_release(&error_buf);
+	}
+
 	fprintf(stderr, "\n Usage: %s\n", *usagestr++);
 	while (*usagestr && **usagestr)
 		fprintf(stderr, "    or: %s\n", *usagestr++);
-- 
2.6.0