Rollup merge of #39065 - frewsxcv:libstd-os-unix-ffi-docs, r=GuillaumeGomez

Add doc examples & description in `std::os::unix::ffi`.

None

Author: GuillaumeGomez

src/libstd/sys/unix/ext/ffi.rs

@@ -20,11 +20,38 @@ use sys_common::{FromInner, IntoInner, AsInner};
 /// Unix-specific extensions to `OsString`.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait OsStringExt {
-    /// Creates an `OsString` from a byte vector.
+    /// Creates an [`OsString`] from a byte vector.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::OsString;
+    /// use std::os::unix::ffi::OsStringExt;
+    ///
+    /// let bytes = b"foo".to_vec();
+    /// let os_string = OsString::from_vec(bytes);
+    /// assert_eq!(os_string.to_str(), Some("foo"));
+    /// ```
+    ///
+    /// [`OsString`]: ../../../ffi/struct.OsString.html
     #[stable(feature = "rust1", since = "1.0.0")]
     fn from_vec(vec: Vec<u8>) -> Self;
 
-    /// Yields the underlying byte vector of this `OsString`.
+    /// Yields the underlying byte vector of this [`OsString`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::OsString;
+    /// use std::os::unix::ffi::OsStringExt;
+    ///
+    /// let mut os_string = OsString::new();
+    /// os_string.push("foo");
+    /// let bytes = os_string.into_vec();
+    /// assert_eq!(bytes, b"foo");
+    /// ```
+    ///
+    /// [`OsString`]: ../../../ffi/struct.OsString.html
     #[stable(feature = "rust1", since = "1.0.0")]
     fn into_vec(self) -> Vec<u8>;
 }
@@ -43,9 +70,36 @@ impl OsStringExt for OsString {
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait OsStrExt {
     #[stable(feature = "rust1", since = "1.0.0")]
+    /// Creates an [`OsStr`] from a byte slice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::OsStr;
+    /// use std::os::unix::ffi::OsStrExt;
+    ///
+    /// let bytes = b"foo";
+    /// let os_str = OsStr::from_bytes(bytes);
+    /// assert_eq!(os_str.to_str(), Some("foo"));
+    /// ```
+    ///
+    /// [`OsStr`]: ../../../ffi/struct.OsStr.html
     fn from_bytes(slice: &[u8]) -> &Self;
 
-    /// Gets the underlying byte view of the `OsStr` slice.
+    /// Gets the underlying byte view of the [`OsStr`] slice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::OsStr;
+    /// use std::os::unix::ffi::OsStrExt;
+    ///
+    /// let mut os_str = OsStr::new("foo");
+    /// let bytes = os_str.as_bytes();
+    /// assert_eq!(bytes, b"foo");
+    /// ```
+    ///
+    /// [`OsStr`]: ../../../ffi/struct.OsStr.html
     #[stable(feature = "rust1", since = "1.0.0")]
     fn as_bytes(&self) -> &[u8];
 }