From 81fdb90e1f2770e35ec10ddd41888bb39162ca51 Mon Sep 17 00:00:00 2001
From: Bobby Bingham <koorogi@koorogi.info>
Date: Mon, 5 Jan 2015 21:16:13 -0600
Subject: improve command line error reporting

---
 src/satmkboot.c | 68 ++++++++++++++++++++++++++++++++-------------------------
 1 file changed, 38 insertions(+), 30 deletions(-)

diff --git a/src/satmkboot.c b/src/satmkboot.c
index 6bd9823..2b7f308 100644
--- a/src/satmkboot.c
+++ b/src/satmkboot.c
@@ -118,62 +118,70 @@ static void usage(const char *progname)
 	fprintf(stderr, "\t%-*s%s\n", width, "-o output",       "Output file");
 }
 
+#define ERR_UNKNOWN_OPTION   0
+#define ERR_MISSING_OPTION   1
+#define ERR_DUPLICATE_INPUT  2
+#define ERR_DUPLICATE_OUTPUT 3
+
+static const char *errmsgs[] = {
+	"Unknown extra argument",
+	"Missing required option",
+	"Duplicate -i parameter",
+	"Duplicate -o parameter",
+};
+
+static int show_arg_error(const char *progname, int prev_errors, int error)
+{
+	if (!(prev_errors & 1 << error))
+		fprintf(stderr, "%s: %s\n", progname, errmsgs[error]);
+	return prev_errors | 1 << error;
+}
+
 static int process_args(int argc, char **argv)
 {
-	int fail = 0, help = 0;
+	int errors = 0, fail = 0, help = 0;
 	int opt;
 
 	extern char *optarg;
 	extern int optind, optopt;
-
-	while ((opt = getopt(argc, argv, ":hi:o:")) != -1) {
+	while ((opt = getopt(argc, argv, "hi:o:")) != -1) {
 		switch (opt) {
 		case 'h':
 			help = 1;
 			break;
 
 		case 'i':
-			if (ipfile) {
-				fprintf(stderr, "Duplicate -i parameter\n");
-				fail = 1;
-			}
-			ipfile = optarg;
+			if (ipfile)
+				errors = show_arg_error(argv[0], errors, ERR_DUPLICATE_INPUT);
+			else
+				ipfile = optarg;
 			break;
 
 		case 'o':
-			if (outfile) {
-				fprintf(stderr, "Duplicate -o parameter\n");
-				fail = 1;
-			}
-			outfile = optarg;
+			if (outfile)
+				errors = show_arg_error(argv[0], errors, ERR_DUPLICATE_OUTPUT);
+			else
+				outfile = optarg;
 			break;
 
-		case ':':
-			fprintf(stderr, "Option '%c' missing required parameter\n", optopt);
-			fail = 1;
-			break;
 
 		default:
-			fprintf(stderr, "Unknown option '%c'\n", opt);
 			fail = 1;
 		}
 	}
 
 	if (help) {
 		usage(argv[0]);
-	} else {
-		if (argv[optind]) {
-			fprintf(stderr, "Unknown extra arguments\n");
-			fail = 1;
-		}
-		if (!ipfile || !outfile) {
-			fprintf(stderr, "Missing required option\n");
-			fail = 1;
-		}
+	} else if (!fail) {
+		if (argv[optind])
+			errors = show_arg_error(argv[0], errors, ERR_UNKNOWN_OPTION);
+		if (!ipfile || !outfile)
+			errors = show_arg_error(argv[0], errors, ERR_MISSING_OPTION);
+		fail = errors;
+	}
 
-		if (fail) {
-			fprintf(stderr, "Use -h option for help on correct usage.\n");
-		}
+	if (fail) {
+		fprintf(stderr, "\nUse -h option for help on correct usage.\n");
 	}
 
 	return fail | help;
-- 
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