add mountpoint

src/uu/mountpoint/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "uu_mountpoint"
+version = "0.0.1"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+
+[[bin]]
+name = "mountpoint"
+path = "src/mountpoint.rs"

src/uu/mountpoint/src/mountpoint.rs

@@ -0,0 +1,42 @@
+// This file is part of the uutils util-linux package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use std::env;
+use std::fs;
+use std::os::unix::fs::MetadataExt;
+use std::process;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+
+    if args.len() != 2 {
+        eprintln!("Usage: mountpoint <path>");
+        process::exit(1);
+    }
+
+    let path = &args[1];
+    if is_mountpoint(path) {
+        println!("{} is a mountpoint", path);
+    } else {
+        println!("{} is not a mountpoint", path);
+    }
+}
+
+fn is_mountpoint(path: &str) -> bool {
+    let metadata = match fs::metadata(path) {
+        Ok(metadata) => metadata,
+        Err(_) => return false,
+    };
+
+    let dev = metadata.dev();
+    let inode = metadata.ino();
+
+    // Root inode (typically 2 in most Unix filesystems) indicates a mount point
+    inode == 2
+        || match fs::metadata("..") {
+            Ok(parent_metadata) => parent_metadata.dev() != dev,
+            Err(_) => false,
+        }
+}