groups: fix argument parsing

groups/groups.rs

@@ -24,24 +24,37 @@ use c_types::{get_pw_from_args, group};
 #[path = "../common/c_types.rs"] mod c_types;
 
 static NAME: &'static str = "groups";
+static VERSION: &'static str = "1.0.0";
 
 #[allow(dead_code)]
 fn main () { os::set_exit_status(uumain(os::args())); }
 
 pub fn uumain(args: Vec<String>) -> int {
+    let program = args.get(0).clone();
+
     let options = [
-            optflag("h", "", "Help")
-        ];
+        optflag("h", "help", "display this help menu and exit"),
+        optflag("V", "version", "display version information and exit")
+    ];
 
     let matches = match getopts(args.tail(), options) {
         Ok(m) => { m },
-        Err(_) => {
-            show_error!("{}", usage(NAME, options));
+        Err(f) => {
+            show_error!("{}", f.to_err_msg());
             return 1;
         }
     };
 
-    group(get_pw_from_args(&matches.free), true);
+    if matches.opt_present("version") {
+        println!("{} v{}", NAME, VERSION);
+    } else if matches.opt_present("help") {
+        print!("{} v{}\n\n\
+                Usage:\n  \
+                  {} [OPTION]... [USER]...\n\n\
+                {}", NAME, VERSION, program, usage("Prints the groups a user is in to standard output.", options));
+    } else {
+        group(get_pw_from_args(&matches.free), true);
+    }
 
     0
 }