std: Allow to spawn a process as a session leader on UNIX

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

@@ -32,6 +32,17 @@ pub trait CommandExt {
     /// the same semantics as the `uid` field.
     #[stable(feature = "rust1", since = "1.0.0")]
     fn gid(&mut self, id: gid_t) -> &mut process::Command;
+
+    /// Create a new session (cf. `setsid(2)`) for the child process. This means that the child is
+    /// the leader of a new process group. The parent process remains the child reaper of the new
+    /// process.
+    ///
+    /// This is not enough to create a daemon process. The *init* process should be the child
+    /// reaper of a daemon. This can be achieved if the parent process exit. Moreover, a daemon
+    /// should not have a controlling terminal. To acheive this, a session leader (the child) must
+    /// spawn another process (the daemon) in the same session.
+    #[unstable(feature = "process_session_leader", reason = "recently added")]
+    fn session_leader(&mut self, on: bool) -> &mut process::Command;
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -45,6 +56,11 @@ impl CommandExt for process::Command {
         self.as_inner_mut().gid = Some(id);
         self
     }
+
+    fn session_leader(&mut self, on: bool) -> &mut process::Command {
+        self.as_inner_mut().session_leader = on;
+        self
+    }
 }
 
 /// Unix-specific extensions to `std::process::ExitStatus`