Add sys users command (#12787)

# Description
Add a new `sys users` command which returns a table of the users of the
system. This is the same table that is currently present as
`(sys).host.sessions`. The same table has been removed from the recently
added `sys host` command.

# User-Facing Changes
Adds a new command. (The old `sys` command is left as is.)

crates/nu-command/src/default_context.rs

@@ -125,6 +125,7 @@ pub fn add_shell_command_context(mut engine_state: EngineState) -> EngineState {
             SysMem,
             SysNet,
             SysTemp,
+            SysUsers,
             UName,
 
         };

crates/nu-command/src/system/sys/host.rs

@@ -26,7 +26,8 @@ impl Command for SysHost {
         call: &Call,
         _input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
-        Ok(super::host(call.head).into_pipeline_data())
+        let host = super::host(call.head);
+        Ok(Value::record(host, call.head).into_pipeline_data())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/system/sys/mod.rs

@@ -5,6 +5,7 @@ mod mem;
 mod net;
 mod sys_;
 mod temp;
+mod users;
 
 pub use cpu::SysCpu;
 pub use disks::SysDisks;
@@ -13,6 +14,7 @@ pub use mem::SysMem;
 pub use net::SysNet;
 pub use sys_::Sys;
 pub use temp::SysTemp;
+pub use users::SysUsers;
 
 use chrono::{DateTime, Local};
 use nu_protocol::{record, Record, Span, Value};
@@ -122,7 +124,29 @@ pub fn mem(span: Span) -> Value {
     Value::record(record, span)
 }
 
-pub fn host(span: Span) -> Value {
+pub fn users(span: Span) -> Value {
+    let users = Users::new_with_refreshed_list()
+        .iter()
+        .map(|user| {
+            let groups = user
+                .groups()
+                .iter()
+                .map(|group| Value::string(trim_cstyle_null(group.name()), span))
+                .collect();
+
+            let record = record! {
+                "name" => Value::string(trim_cstyle_null(user.name()), span),
+                "groups" => Value::list(groups, span),
+            };
+
+            Value::record(record, span)
+        })
+        .collect();
+
+    Value::list(users, span)
+}
+
+pub fn host(span: Span) -> Record {
     let mut record = Record::new();
 
     if let Some(name) = System::name() {
@@ -160,27 +184,7 @@ pub fn host(span: Span) -> Value {
     let timestamp_str = datetime.with_timezone(datetime.offset()).to_rfc3339();
     record.push("boot_time", Value::string(timestamp_str, span));
 
-    let users = Users::new_with_refreshed_list()
-        .iter()
-        .map(|user| {
-            let groups = user
-                .groups()
-                .iter()
-                .map(|group| Value::string(trim_cstyle_null(group.name()), span))
-                .collect();
-
-            let record = record! {
-                "name" => Value::string(trim_cstyle_null(user.name()), span),
-                "groups" => Value::list(groups, span),
-            };
-
-            Value::record(record, span)
-        })
-        .collect();
-
-    record.push("sessions", Value::list(users, span));
-
-    Value::record(record, span)
+    record
 }
 
 pub fn temp(span: Span) -> Value {

crates/nu-command/src/system/sys/sys_.rs

@@ -43,8 +43,11 @@ impl Command for Sys {
         );
 
         let head = call.head;
+
+        let mut host = super::host(head);
+        host.push("sessions", super::users(head));
         let record = record! {
-            "host" => super::host(head),
+            "host" => Value::record(host, head),
             "cpu" => super::cpu(head),
             "disks" => super::disks(head),
             "mem" => super::mem(head),

crates/nu-command/src/system/sys/users.rs

@@ -0,0 +1,38 @@
+use nu_engine::command_prelude::*;
+
+#[derive(Clone)]
+pub struct SysUsers;
+
+impl Command for SysUsers {
+    fn name(&self) -> &str {
+        "sys users"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("sys users")
+            .category(Category::System)
+            .input_output_types(vec![(Type::Nothing, Type::record())])
+    }
+
+    fn usage(&self) -> &str {
+        "View information about the users on the system."
+    }
+
+    fn run(
+        &self,
+        _engine_state: &EngineState,
+        _stack: &mut Stack,
+        call: &Call,
+        _input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        Ok(super::users(call.head).into_pipeline_data())
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Show info about the system users",
+            example: "sys users",
+            result: None,
+        }]
+    }
+}