getopt

date.c

@@ -1,29 +1,30 @@
 /* See LICENSE file for copyright and license details. */
 #include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
 #include <time.h>
+#include <unistd.h>
 #include "util.h"
 
 int
 main(int argc, char *argv[])
 {
-	char buf[BUFSIZ];
+	char buf[BUFSIZ], c;
 	char *fmt = "%c";
-	int i;
 	struct tm *now = NULL;
 	time_t t;
 
 	t = time(NULL);
-	for(i = 1; i < argc; i++)
-		if(!strncmp("+", argv[i], 1))
-			fmt = &argv[i][1];
-		else if(!strcmp("-d", argv[i]) && i+1 < argc)
-			t = strtol(argv[++i], NULL, 0);
-		else
-			eprintf("usage: %s [-d time] [+format]\n", argv[0]);
-	now = localtime(&t);
-	if(!now)
+	while((c = getopt(argc, argv, "d:")) != -1)
+		switch(c) {
+		case 'd':
+			t = strtol(optarg, NULL, 0);
+			break;
+		default:
+			exit(EXIT_FAILURE);
+		}
+	if(optind < argc && argv[optind][0] == '+')
+		fmt = &argv[optind][1];
+	if(!(now = localtime(&t)))
 		eprintf("localtime failed\n");
 
 	strftime(buf, sizeof buf, fmt, now);