Merge #1133

1133: Implement mkfifoat  r=asomers a=zmlcc

This adds the `mkfifoat ` function, which is part of POSIX [https://pubs.opengroup.org/onlinepubs/9699919799/functions/mkfifoat.html](https://pubs.opengroup.org/onlinepubs/9699919799/functions/mkfifoat.html)

test cases are copied from `mkfifo`


Co-authored-by: Zhang Miaolei <zmlcc@outlook.com>

CHANGELOG.md

@@ -15,6 +15,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Added `NixPath::is_empty`.
   ([#1107](https://github.com/nix-rust/nix/pull/1107))
 
+- Added `mkfifoat`
+  ([#1133](https://github.com/nix-rust/nix/pull/1133))
+
 ### Changed
 - `Signal::from_c_int` has been replaced by `Signal::try_from`
   ([#1113](https://github.com/nix-rust/nix/pull/1113))

src/unistd.rs

@@ -506,6 +506,26 @@ pub fn mkfifo<P: ?Sized + NixPath>(path: &P, mode: Mode) -> Result<()> {
     Errno::result(res).map(drop)
 }
 
+/// Creates new fifo special file (named pipe) with path `path` and access rights `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
+/// 
+/// [mkfifoat(2)](http://pubs.opengroup.org/onlinepubs/9699919799/functions/mkfifoat.html).
+// mkfifoat is not implemented in OSX or android
+#[inline]
+#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "android")))]
+pub fn mkfifoat<P: ?Sized + NixPath>(dirfd: Option<RawFd>, path: &P, mode: Mode) -> Result<()> {
+    let res = path.with_nix_path(|cstr| unsafe {
+        libc::mkfifoat(at_rawfd(dirfd), cstr.as_ptr(), mode.bits() as mode_t)
+    })?;
+
+    Errno::result(res).map(drop)
+}
+
 /// Creates a symbolic link at `path2` which points to `path1`.
 ///
 /// If `dirfd` has a value, then `path2` is relative to directory associated

test/test_unistd.rs

@@ -98,6 +98,58 @@ fn test_mkfifo_directory() {
     assert!(mkfifo(&env::temp_dir(), Mode::S_IRUSR).is_err());
 }
 
+#[test]
+#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "android")))]
+fn test_mkfifoat_none() {
+    let tempdir = tempfile::tempdir().unwrap();
+    let mkfifoat_fifo = tempdir.path().join("mkfifoat_fifo");
+
+    mkfifoat(None, &mkfifoat_fifo, Mode::S_IRUSR).unwrap();
+
+    let stats = stat::stat(&mkfifoat_fifo).unwrap();
+    let typ = stat::SFlag::from_bits_truncate(stats.st_mode);
+    assert_eq!(typ, SFlag::S_IFIFO);
+}
+
+#[test]
+#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "android")))]
+fn test_mkfifoat() {
+    let tempdir = tempfile::tempdir().unwrap();
+    let dirfd = open(tempdir.path(), OFlag::empty(), Mode::empty()).unwrap();
+    let mkfifoat_name = "mkfifoat_name";
+
+    mkfifoat(Some(dirfd), mkfifoat_name, Mode::S_IRUSR).unwrap();
+
+    let stats = stat::fstatat(dirfd, mkfifoat_name, fcntl::AtFlags::empty()).unwrap();
+    let typ = stat::SFlag::from_bits_truncate(stats.st_mode);
+    assert_eq!(typ, SFlag::S_IFIFO);
+}
+
+#[test]
+#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "android")))]
+fn test_mkfifoat_directory_none() {
+    // mkfifoat should fail if a directory is given
+    assert_eq!(
+        mkfifoat(None, &env::temp_dir(), Mode::S_IRUSR).is_ok(),
+        false
+    );
+}
+
+#[test]
+#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "android")))]
+fn test_mkfifoat_directory() {
+    // mkfifoat should fail if a directory is given
+    let tempdir = tempfile::tempdir().unwrap();
+    let dirfd = open(tempdir.path(), OFlag::empty(), Mode::empty()).unwrap();
+    let mkfifoat_dir = "mkfifoat_dir";
+    stat::mkdirat(dirfd, mkfifoat_dir, Mode::S_IRUSR).unwrap();
+
+    assert_eq!(
+        mkfifoat(Some(dirfd), mkfifoat_dir, Mode::S_IRUSR).is_ok(),
+        false
+    );
+}
+
 #[test]
 fn test_getpid() {
     let pid: ::libc::pid_t = getpid().into();