Make $nu constant (#10160)

crates/nu-system/src/lib.rs

@@ -3,6 +3,7 @@ mod foreground;
 mod linux;
 #[cfg(target_os = "macos")]
 mod macos;
+pub mod os_info;
 #[cfg(target_os = "windows")]
 mod windows;
 

crates/nu-system/src/os_info.rs

@@ -0,0 +1,21 @@
+use sysinfo::SystemExt;
+
+pub fn get_os_name() -> &'static str {
+    std::env::consts::OS
+}
+
+pub fn get_os_arch() -> &'static str {
+    std::env::consts::ARCH
+}
+
+pub fn get_os_family() -> &'static str {
+    std::env::consts::FAMILY
+}
+
+pub fn get_kernel_version() -> String {
+    let sys = sysinfo::System::new();
+    match sys.kernel_version() {
+        Some(v) => v,
+        None => "unknown".to_string(),
+    }
+}