address more review comments

* s/descriptor/file descriptor/ in a comment
* allow passing through a mode in Dir::open/openat; at least on Linux,
  it's possible to create a new directory with open/openat rather than
  using mkdir/mkdirat.

src/dir.rs

@@ -18,7 +18,7 @@ use libc::{dirent, readdir_r};
 ///    * can be opened from a file descriptor (as returned by `openat`, perhaps before knowing
 ///      if the path represents a file or directory).
 ///    * implements `AsRawFd`, so it can be passed to `fstat`, `openat`, etc.
-///      The descriptor continues to be owned by the `Dir`, so callers must not keep a `RawFd`
+///      The file descriptor continues to be owned by the `Dir`, so callers must not keep a `RawFd`
 ///      after the `Dir` is dropped.
 ///    * can be iterated through multiple times without closing and reopening the file
 ///      descriptor. Each iteration rewinds when finished.
@@ -32,14 +32,16 @@ pub struct Dir(
 
 impl Dir {
     /// Opens the given path as with `fcntl::open`.
-    pub fn open<P: ?Sized + NixPath>(path: &P, oflag: OFlag) -> Result<Self> {
-        let fd = fcntl::open(path, oflag, sys::stat::Mode::empty())?;
+    pub fn open<P: ?Sized + NixPath>(path: &P, oflag: OFlag,
+                                     mode: sys::stat::Mode) -> Result<Self> {
+        let fd = fcntl::open(path, oflag, mode)?;
         Dir::from_fd(fd)
     }
 
     /// Opens the given path as with `fcntl::openat`.
-    pub fn openat<P: ?Sized + NixPath>(dirfd: RawFd, path: &P, oflag: OFlag) -> Result<Self> {
-        let fd = fcntl::openat(dirfd, path, oflag, sys::stat::Mode::empty())?;
+    pub fn openat<P: ?Sized + NixPath>(dirfd: RawFd, path: &P, oflag: OFlag,
+                                       mode: sys::stat::Mode) -> Result<Self> {
+        let fd = fcntl::openat(dirfd, path, oflag, mode)?;
         Dir::from_fd(fd)
     }
 

test/test_dir.rs

@@ -3,6 +3,7 @@ extern crate tempdir;
 
 use nix::dir::{Dir, Type};
 use nix::fcntl::OFlag;
+use nix::sys::stat::Mode;
 use std::fs::File;
 use self::tempdir::TempDir;
 
@@ -11,8 +12,8 @@ fn read() {
     let tmp = TempDir::new("nix-dir-read").unwrap();
     File::create(&tmp.path().join("foo")).unwrap();
     ::std::os::unix::fs::symlink("foo", tmp.path().join("bar")).unwrap();
-    let mut dir =
-        Dir::open(tmp.path(), OFlag::O_DIRECTORY | OFlag::O_RDONLY | OFlag::O_CLOEXEC).unwrap();
+    let mut dir = Dir::open(tmp.path(), OFlag::O_DIRECTORY | OFlag::O_RDONLY | OFlag::O_CLOEXEC,
+                            Mode::empty()).unwrap();
     let mut entries: Vec<_> = dir.iter().map(|e| e.unwrap()).collect();
     entries.sort_by(|a, b| a.file_name().cmp(b.file_name()));
     let entry_names: Vec<_> = entries
@@ -32,8 +33,8 @@ fn read() {
 #[test]
 fn rewind() {
     let tmp = TempDir::new("nix-dir-rewind").unwrap();
-    let mut dir =
-        Dir::open(tmp.path(), OFlag::O_DIRECTORY | OFlag::O_RDONLY | OFlag::O_CLOEXEC).unwrap();
+    let mut dir = Dir::open(tmp.path(), OFlag::O_DIRECTORY | OFlag::O_RDONLY | OFlag::O_CLOEXEC,
+                            Mode::empty()).unwrap();
     let entries1: Vec<_> = dir.iter().map(|e| e.unwrap().file_name().to_owned()).collect();
     let entries2: Vec<_> = dir.iter().map(|e| e.unwrap().file_name().to_owned()).collect();
     assert_eq!(entries1, entries2);