selftests/bpf: emit processing progress and add quiet mode to veristat

Emit "Processing <filepath>..." for each BPF object file to be
processed, to show progress. But also add -q (--quiet) flag to silence
such messages. Doing something more clever (like overwriting same output
line) is to cumbersome and easily breakable if there is any other
console output (e.g., errors from libbpf).

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220923175913.3272430-5-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/veristat.c

@@ -63,6 +63,7 @@ static struct env {
 	char **filenames;
 	int filename_cnt;
 	bool verbose;
+	bool quiet;
 	enum resfmt out_fmt;
 	bool comparison_mode;
 
@@ -107,6 +108,7 @@ const char argp_program_doc[] =
 static const struct argp_option opts[] = {
 	{ NULL, 'h', NULL, OPTION_HIDDEN, "Show the full help" },
 	{ "verbose", 'v', NULL, 0, "Verbose mode" },
+	{ "quiet", 'q', NULL, 0, "Quiet mode" },
 	{ "emit", 'e', "SPEC", 0, "Specify stats to be emitted" },
 	{ "sort", 's', "SPEC", 0, "Specify sort order" },
 	{ "output-format", 'o', "FMT", 0, "Result output format (table, csv), default is table." },
@@ -131,6 +133,9 @@ static error_t parse_arg(int key, char *arg, struct argp_state *state)
 	case 'v':
 		env.verbose = true;
 		break;
+	case 'q':
+		env.quiet = true;
+		break;
 	case 'e':
 		err = parse_stats(arg, &env.output_spec);
 		if (err)
@@ -569,8 +574,10 @@ static int process_obj(const char *filename)
 		return 0;
 	}
 
-	old_libbpf_print_fn = libbpf_set_print(libbpf_print_fn);
+	if (!env.quiet && env.out_fmt == RESFMT_TABLE)
+		printf("Processing '%s'...\n", basename(filename));
 
+	old_libbpf_print_fn = libbpf_set_print(libbpf_print_fn);
 	obj = bpf_object__open_file(filename, &opts);
 	if (!obj) {
 		/* if libbpf can't open BPF object file, it could be because
@@ -1268,6 +1275,12 @@ int main(int argc, char **argv)
 	if (argp_parse(&argp, argc, argv, 0, NULL, NULL))
 		return 1;
 
+	if (env.verbose && env.quiet) {
+		fprintf(stderr, "Verbose and quiet modes are incompatible, please specify just one or neither!\n");
+		argp_help(&argp, stderr, ARGP_HELP_USAGE, "veristat");
+		return 1;
+	}
+
 	if (env.output_spec.spec_cnt == 0)
 		env.output_spec = default_output_spec;
 	if (env.sort_spec.spec_cnt == 0)