From eb7115b77e55fb049edd5582b114eefb246edf40 Mon Sep 17 00:00:00 2001
From: Patrick McDermott <patrick.mcdermott@libiquity.com>
Date: Thu, 18 Jul 2019 14:33:45 -0400
Subject: main(): Print usage

---
diff --git a/src/main.c b/src/main.c
index 6825179..411902c 100644
--- a/src/main.c
+++ b/src/main.c
@@ -28,6 +28,18 @@
 #include "image.h"
 #include "text.h"
 
+static void
+usage(FILE *stream, const char *program_name)
+{
+	fprintf(stream, _("Usage: %s [-f <font>] [-w <width>] [-h <height>] "
+				"<text-input> <png-output>\n"), program_name);
+	fputs(_("  -f <font>    name of font face, or \"list\" to list "
+				"available font face names\n"), stream);
+	fputs(_("  -w <width>   width of image in character columns\n"),
+			stream);
+	fputs(_("  -h <height>  height of image in character rows\n"), stream);
+}
+
 int
 main(int argc, char **argv)
 {
@@ -50,31 +62,37 @@ main(int argc, char **argv)
 			case 'f':
 				font = font_find(optarg);
 				if (!font) {
-					printf(_("Font \"%s\" not found\n"),
+					fprintf(stderr, _("Font \"%s\" not "
+								"found\n"),
 							optarg);
+					usage(stderr, argv[0]);
 					return 1;
 				}
 				break;
 			case 'w':
 				w = strtol(optarg, &end, 10);
 				if (*optarg == '\0' || *end != '\0' || w <= 0) {
-					printf(_("Width must be an integer "
+					fprintf(stderr, _("Width must be an "
+								"integer "
 								"greater than "
 								"0\n"));
+					usage(stderr, argv[0]);
 					return 1;
 				}
 				break;
 			case 'h':
 				h = strtol(optarg, &end, 10);
 				if (*optarg == '\0' || *end != '\0' || h <= 0) {
-					printf(_("Height must be an integer "
+					fprintf(stderr, _("Height must be an "
+								"integer "
 								"greater than "
 								"0\n"));
+					usage(stderr, argv[0]);
 					return 1;
 				}
 				break;
 			default:
-				printf(_("Invalid option\n"));
+				usage(stderr, argv[0]);
 				return 1;
 		}
 	}
@@ -91,8 +109,8 @@ main(int argc, char **argv)
 	if (strcmp(input, "-") != 0) {
 		fp = fopen(input, "r");
 		if (!fp) {
-			printf(_("Error: Cannot open \"%s\" for reading\n"),
-					input);
+			fprintf(stderr, _("Error: Cannot open \"%s\" for "
+						"reading\n"), input);
 			return 1;
 		}
 	} else {
--
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