Add a mkfifoat function (#1399)

Author: rusty-snake

src/fs/at.rs

@@ -469,6 +469,24 @@ pub fn mknodat<P: path::Arg, Fd: AsFd>(
     })
 }
 
+/// `mkfifoat(dirfd, path, mode)`—Make a FIFO special file.
+///
+/// # References
+///  - [POSIX]
+///
+/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/mkfifoat.html
+#[cfg(not(any(
+    apple,
+    target_os = "espidf",
+    target_os = "horizon",
+    target_os = "vita",
+    target_os = "wasi"
+)))]
+#[inline]
+pub fn mkfifoat<P: path::Arg, Fd: AsFd>(dirfd: Fd, path: P, mode: Mode) -> io::Result<()> {
+    mknodat(dirfd, path, FileType::Fifo, mode, 0)
+}
+
 /// `fchownat(dirfd, path, owner, group, flags)`—Sets file or directory
 /// ownership.
 ///