Add OpenOptionsExt doc examples

src/libstd/sys/unix/ext/fs.rs

@@ -25,15 +25,53 @@ use sys::platform::fs::MetadataExt as UnixMetadataExt;
 pub trait PermissionsExt {
  /// Returns the underlying raw `mode_t` bits that are the standard Unix
  /// permissions for this file.
+ ///
+ /// # Examples
+ ///
+ /// ```rust,ignore
+ /// use std::fs::File;
+ /// use std::os::unix::fs::PermissionsExt;
+ ///
+ /// let f = try!(File::create("foo.txt"));
+ /// let metadata = try!(f.metadata());
+ /// let permissions = metadata.permissions();
+ ///
+ /// println!("permissions: {}", permissions.mode());
+ /// ```
  #[stable(feature = "fs_ext", since = "1.1.0")]
  fn mode(&self) -> u32;
 
  /// Sets the underlying raw bits for this set of permissions.
+ ///
+ /// # Examples
+ ///
+ /// ```rust,ignore
+ /// use std::fs::File;
+ /// use std::os::unix::fs::PermissionsExt;
+ ///
+ /// let f = try!(File::create("foo.txt"));
+ /// let metadata = try!(f.metadata());
+ /// let mut permissions = metadata.permissions();
+ ///
+ /// permissions.set_mode(0o644); // Read/write for owner and read for others.
+ /// assert_eq!(permissions.mode(), 0o644);
+ /// ```
  #[stable(feature = "fs_ext", since = "1.1.0")]
  fn set_mode(&mut self, mode: u32);
 
  /// Creates a new instance of `Permissions` from the given set of Unix
  /// permission bits.
+ ///
+ /// # Examples
+ ///
+ /// ```rust,ignore
+ /// use std::fs::Permissions;
+ /// use std::os::unix::fs::PermissionsExt;
+ ///
+ /// // Read/write for owner and read for others.
+ /// let permissions = Permissions::from_mode(0o644);
+ /// assert_eq!(permissions.mode(), 0o644);
+ /// ```
  #[stable(feature = "fs_ext", since = "1.1.0")]
  fn from_mode(mode: u32) -> Self;
 }