added help message

us.c

@@ -87,7 +87,7 @@ struct user_info {
 static void *emalloc(size_t);
 static char *estrdup(const char *);
 void *erealloc(void *, size_t);
-static void usage(void);
+static void usage(int);
 static void die(const char *, ...);
 static int perm_set(struct passwd *, struct group *);
 static int authenticate(uid_t, int, int);
@@ -106,7 +106,7 @@ int main(int argc, char *argv[])
 	struct user_info t_gr_info = {0}, t_pw_info = {0};
 	int opt, err;
 	int shellflag = 0, envflag = 0, askpass = 0;
-	while ((opt = getopt(argc, argv, "Au:g:C:se")) != -1) {
+	while ((opt = getopt(argc, argv, "Au:g:C:seh")) != -1) {
 		switch (opt) {
 		case 'A':
 			askpass = 1;
@@ -126,8 +126,12 @@ int main(int argc, char *argv[])
 		case 'e':
 			envflag = 1;
 			break;
+		case 'h':
+			usage(1);
+			exit(EXIT_SUCCESS);
+			break;
 		case '?':
-			usage();
+			usage(0);
 			exit(EINVAL);
 			break;
 		}
@@ -368,17 +372,18 @@ int main(int argc, char *argv[])
 	return errno;
 }
 
-static inline void usage(void)
+static inline void usage(int complete)
 {
-	// TODO: planned options
-	// -a [program]: like sudo's askpass
-	// -u [user]: change the default user from root to user
-	// -g [group]: change the primary group to [gorup]
-	// 	both -a and -g will accept numbers with #[num] like sudo
-	// -c [file]: manually select config file
-	// something about environment
-	// something about non interactiveness
-	printf("usage: us [-seA] [-u user] [-g group] [-C config] command [args]\n");
+	printf("usage: us [-hseA] [-u user] [-g group] [-C config] command [args]\n");
+	if (!complete)
+		return;
+	printf("-h        print this message\n"
+	       "-s        use the user's shell instead of /bin/sh\n"
+	       "-e        keep the user's entire environment\n"
+	       "-A        use the command in US_ASKPASS as askpass helper\n"
+	       "-u user   set new user to 'user' instead of root\n"
+	       "-s group  set new group to 'group'\n"
+	       "-C config use specifi config file\n");
 }
 
 static int perm_set(struct passwd *pw, struct group *gr)