Accept no argument along with - for stdin

README.md

@@ -24,7 +24,8 @@ Usage
 
     hostsblock [filterlist]
 
-If the filterlist argument is `-`, hostsblock will read from stdin. For example,
+If the filterlist argument is `-` or omitted, hostsblock will read from stdin.
+For example,
 
     curl -s https://www.fanboy.co.nz/r/fanboy-ultimate.txt | hostsblock -
 
@@ -33,4 +34,6 @@ list, read the hosts file entries from it with hostsblock, and concatenate the
 original hosts file with the ad-blocking entries to create the actual hosts
 file:
 
-    curl -s https://www.fanboy.co.nz/r/fanboy-ultimate.txt | hostsblock - | cat /etc/hosts~ - > /etc/hosts
+    curl -s https://www.fanboy.co.nz/r/fanboy-ultimate.txt |
+    hostsblock |
+    cat /etc/hosts~ - > /etc/hosts

hostsblock.c

@@ -114,12 +114,12 @@ int main(int argc, char **argv)
 	char rule[MAX_DOMAIN_RULE_LENGTH];
 	char domain[MAX_DOMAIN_LENGTH] = { 0 };
 
-	if (argc != 2) {
+	if (argc > 2) {
 		fprintf(stderr, "usage: %s [filterlist]\n", argv[0]);
 		return 1;
 	}
-
-	if (!strncmp(argv[1], "-", 2)) list = stdin;
+	
+	if (argc < 2 || !strncmp(argv[1], "-", 2)) list = stdin;
 	else list = fopen(argv[1], "r");
 
 	if (list == NULL) {