Implement faccessat

CHANGELOG.md

@@ -17,6 +17,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 - Added `mkfifoat`
   ([#1133](https://github.com/nix-rust/nix/pull/1133))
+
+- Added `faccessat`
+  ([#1134](https://github.com/nix-rust/nix/pull/1134))
 
 ### Changed
 - `Signal::from_c_int` has been replaced by `Signal::try_from`

src/unistd.rs

@@ -2424,3 +2424,21 @@ pub fn access<P: ?Sized + NixPath>(path: &P, amode: AccessFlags) -> Result<()> {
     })?;
     Errno::result(res).map(drop)
 }
+
+/// Checks the file named by `path` for accessibility according to the flags given by `mode`
+/// 
+/// If `dirfd` has a value, then `path` is relative to directory associated with the file descriptor.
+/// 
+/// If `dirfd` is `None`, then `path` is relative to the current working directory.
+/// 
+/// # References
+/// 
+/// [faccessat(2)](http://pubs.opengroup.org/onlinepubs/9699919799/functions/faccessat.html)
+pub fn faccessat<P: ?Sized + NixPath>(dirfd: Option<RawFd>, path: &P, mode: AccessFlags, flag: AtFlags) -> Result<()> {
+    let res = path.with_nix_path(|cstr| {
+        unsafe {
+            libc::faccessat(at_rawfd(dirfd), cstr.as_ptr(), mode.bits(), flag.bits())
+        }
+    })?;
+    Errno::result(res).map(drop)
+}

test/test_unistd.rs

@@ -727,3 +727,71 @@ fn test_access_file_exists() {
     let _file = File::create(path.clone()).unwrap();
     assert!(access(&path, AccessFlags::R_OK | AccessFlags::W_OK).is_ok());
 }
+
+#[test]
+fn test_faccessat_none_not_existing() {
+    use nix::fcntl::AtFlags;
+    let tempdir = tempfile::tempdir().unwrap();
+    let dir = tempdir.path().join("does_not_exist.txt");
+    assert_eq!(
+        faccessat(None, &dir, AccessFlags::F_OK, AtFlags::empty())
+            .err()
+            .unwrap()
+            .as_errno()
+            .unwrap(),
+        Errno::ENOENT
+    );
+}
+
+#[test]
+fn test_faccessat_not_existing() {
+    use nix::fcntl::AtFlags;
+    let tempdir = tempfile::tempdir().unwrap();
+    let dirfd = open(tempdir.path(), OFlag::empty(), Mode::empty()).unwrap();
+    let not_exist_file = "does_not_exist.txt";
+    assert_eq!(
+        faccessat(
+            Some(dirfd),
+            not_exist_file,
+            AccessFlags::F_OK,
+            AtFlags::empty()
+        )
+        .err()
+        .unwrap()
+        .as_errno()
+        .unwrap(),
+        Errno::ENOENT
+    );
+}
+
+#[test]
+fn test_faccessat_none_file_exists() {
+    use nix::fcntl::AtFlags;
+    let tempdir = tempfile::tempdir().unwrap();
+    let path = tempdir.path().join("does_exist.txt");
+    let _file = File::create(path.clone()).unwrap();
+    assert!(faccessat(
+        None,
+        &path,
+        AccessFlags::R_OK | AccessFlags::W_OK,
+        AtFlags::empty()
+    )
+    .is_ok());
+}
+
+#[test]
+fn test_faccessat_file_exists() {
+    use nix::fcntl::AtFlags;
+    let tempdir = tempfile::tempdir().unwrap();
+    let dirfd = open(tempdir.path(), OFlag::empty(), Mode::empty()).unwrap();
+    let exist_file = "does_exist.txt";
+    let path = tempdir.path().join(exist_file);
+    let _file = File::create(path.clone()).unwrap();
+    assert!(faccessat(
+        Some(dirfd),
+        &path,
+        AccessFlags::R_OK | AccessFlags::W_OK,
+        AtFlags::empty()
+    )
+    .is_ok());
+}