Add permissions to the filesystem, preliminary permissions to the syscalls

programs/id/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "id"
+version = "0.1.0"
+
+[dependencies]
+syscall = { path = "../../syscall/" }

programs/id/src/main.rs

@@ -0,0 +1,11 @@
+#![feature(question_mark)]
+
+extern crate syscall;
+
+use std::env;
+
+pub fn main() {
+    let uid = syscall::getuid().expect("id: failed to get UID");
+    let gid = syscall::getgid().expect("id: failed to get GID");
+    println!("uid={}({}) gid={}({})", uid, env::var("USER").unwrap_or(String::new()), gid, "");
+}