Fix more opts.

src/main.rs

@@ -14,24 +14,32 @@ use byteorder::{ReadBytesExt, WriteBytesExt, LittleEndian};
 
 fn main() {
     let args: Vec<String> = env::args().collect();
+    let program = args[0].clone();
 
     let mut opts = Options::new();
 
-    opts.optflag("c", "", "Compress file");
+    opts.optflag("c", "", "compress file");
-    opts.optflag("x", "", "Extract file");
+    opts.optflag("d", "", "decompress file");
+    opts.optflag("h", "help", "display this help and exit");
 
     let matches = match opts.parse(&args[1..]) {
         Ok(m) => { m }
         Err(f) => { panic!(f.to_string()) }
     };
 
+    if matches.opt_present("help") {
+        let brief = format!("Usage: {} [option] INPUT OUTPUT", program);
+        print!("{}", opts.usage(&brief));
+        return;
+    }
+
     if matches.opt_present("c") {
         let input = &matches.free[0];
         let output = &matches.free[1];
 
-        create(&input, &output);
+        compress(&input, &output);
     }
-    else if matches.opt_present("x") {
+    else if matches.opt_present("d") {
         let input = &matches.free[0];
         let output = &matches.free[1];
 
@@ -39,7 +47,7 @@ fn main() {
     }
 }
 
-fn create(input: &String, output: &String) {
+fn compress(input: &String, output: &String) {
     let mut output_file = fs::File::create(output).unwrap();
 
     let input_file = fs::File::open(input).unwrap();