cat(1p): fix unbuffered output

src/cat.c

@@ -28,9 +28,9 @@
 #include <unistd.h>
 
 int main(int argc, char *argv[]) {
-	int i = 1;
 	bool u = false;
-
+	int opt;
+	FILE *file;
 	char *usage_text = "(-u) [file...]";
 	int buf_size = strlen(argv[0]) + strlen("Usage: ") + strlen(usage_text) + 3;
 	char *usage = calloc(buf_size, buf_size);
@@ -39,8 +39,7 @@ int main(int argc, char *argv[]) {
 		snprintf(usage, buf_size, "Usage: %s (-u) [file...]\n", argv[0])
 	) < 0 ) {}
 
-	int opt;
-
+	extern int optind;
 	while ((opt = getopt(argc, argv, "u")) != -1) {
 		switch(opt) {
 			/*
@@ -50,17 +49,17 @@ int main(int argc, char *argv[]) {
 			 *           without delay as each is read.
 			 */
 			case 'u':
-				i = 2;
 				u = true;
 				break;
 			default:
 				break;
 		}
 	}
+	argv += optind;
+	argc -= optind;
 
-	FILE *file;
-
-	for (; i <= (argc - 1); i++) {
+	for (int i = 0; i < argc; i++) {
+		int byte = 0;
 	  /*
 		 * From cat(1p):
 		 *
@@ -72,33 +71,24 @@ int main(int argc, char *argv[]) {
 		 *           but shall accept multiple occurrences of '-' as a file
 		 *           operand.
 		 */
-		printf("argv[%d]: %s\n", i, argv[i]);
-		if (argv[i] == "-" || u && (argc - 1) == 1 || !u && argc == 1) {
-			file = fdopen(0, "r");
+		if (argv[i] == "-" || argc == 0) {
+			file = stdin;
 		} else if ((file = fopen(argv[i], "r")) == NULL) {
 			// TODO: Add error handling
 			fputs(usage, stderr);
 			return EX_NOINPUT;
 		}
 
-		int byte = 0;
-
-		if (u) {
-			while (byte != EOF) {
-				byte = fgetc(file);
+		for (char *buf = calloc(4096, 1); byte != EOF; fputs(buf, stdout)) {
+			byte = fgetc(file);
+			if (u) {
 				putchar(byte);
-			}
-		} else {
-			char *buf = calloc(1, 4096);
-			while (byte != EOF) {
-				byte = fgetc(file);
-				fputc(byte, fdopen(1, "r"));
+			} else {
+				snprintf(buf, 4096, "%c", byte);
 			}
 		}
-		if (fclose(file) == -1) {
-			fprintf(stderr, "%s: %s: Error closing file.\n", argv[0], argv[i]);
-			return EX_OSERR;
-		}
+
+		if (file != stdin) { fclose(file); }
 	}
 
 	return EX_OK;