skip if already exists.

src/main.rs

@@ -10,6 +10,8 @@ fn unar_file(path: &Path) -> io::Result<()> {
     let filename = path.file_name().unwrap();
     let output = Command::new("unar")
         .current_dir(parent_dir)
+        .arg("-s")
+        .arg("-d")
         .arg(filename)
         .output();