top: implement user count

src/uu/top/Cargo.toml

@@ -22,6 +22,12 @@ chrono = { workspace = true }
 systemstat = { workspace = true }
 bytesize = { workspace = true }
 
+[target.'cfg(target_os="linux")'.dependencies]
+libsystemd-sys = "0.9.3"
+
+[target.'cfg(target_os="windows")'.dependencies]
+windows = { version = "0.59.0", features = ["Win32_System_RemoteDesktop"] }
+
 [lib]
 path = "src/top.rs"
 

src/uu/top/src/header.rs

@@ -51,6 +51,7 @@ pub(crate) fn header(arg: &ArgMatches) -> String {
     )
 }
 
+#[cfg(not(target_os = "linux"))]
 fn todo() -> String {
     "TODO".into()
 }
@@ -85,9 +86,121 @@ fn uptime() -> String {
     res
 }
 
-//TODO: Implement active user count
+fn format_user(user: u64) -> String {
+    match user {
+        0 => "0 user".to_string(),
+        1 => "1 user".to_string(),
+        _ => format!("{} users", user),
+    }
+}
+
+#[cfg(target_os = "windows")]
 fn user() -> String {
-    todo()
+    use windows::{core::*, Win32::System::RemoteDesktop::*};
+
+    let mut num_user = 0;
+
+    unsafe {
+        let mut session_info_ptr = std::ptr::null_mut();
+        let mut session_count = 0;
+
+        WTSEnumerateSessionsW(
+            Some(WTS_CURRENT_SERVER_HANDLE),
+            0,
+            1,
+            &mut session_info_ptr,
+            &mut session_count,
+        )
+        .unwrap();
+
+        let sessions = std::slice::from_raw_parts(session_info_ptr, session_count as usize);
+
+        for session in sessions {
+            let mut buffer = PWSTR::null();
+            let mut bytes_returned = 0;
+
+            WTSQuerySessionInformationW(
+                Some(WTS_CURRENT_SERVER_HANDLE),
+                session.SessionId,
+                WTS_INFO_CLASS(5),
+                &mut buffer,
+                &mut bytes_returned,
+            )
+            .unwrap();
+
+            let username = PWSTR(buffer.0).to_string().unwrap_or_default();
+            if !username.is_empty() {
+                num_user += 1;
+            }
+
+            WTSFreeMemory(buffer.0 as _);
+        }
+
+        WTSFreeMemory(session_info_ptr as _);
+    }
+
+    format_user(num_user)
+}
+
+#[cfg(unix)]
+// see: https://gitlab.com/procps-ng/procps/-/blob/4740a0efa79cade867cfc7b32955fe0f75bf5173/library/uptime.c#L63-L115
+fn user() -> String {
+    use libc::{endutxent, getutxent, setutxent};
+
+    unsafe {
+        #[cfg(target_os = "linux")]
+        {
+            use libc::free;
+            use libsystemd_sys::daemon::sd_booted;
+            use libsystemd_sys::login::{sd_get_sessions, sd_session_get_class};
+            use std::ffi::{c_char, c_void, CStr};
+            use std::ptr;
+            // systemd
+            if sd_booted() > 0 {
+                let mut sessions_list: *mut *mut c_char = ptr::null_mut();
+                let mut num_user = 0;
+                let sessions = sd_get_sessions(&mut sessions_list); // rust-systemd does not implement this
+
+                if sessions > 0 {
+                    for i in 0..sessions {
+                        let mut class: *mut c_char = ptr::null_mut();
+
+                        if sd_session_get_class(
+                            *sessions_list.add(i as usize) as *const c_char,
+                            &mut class,
+                        ) < 0
+                        {
+                            continue;
+                        }
+                        if CStr::from_ptr(class).to_str().unwrap().starts_with("user") {
+                            num_user += 1;
+                        }
+                        free(class as *mut c_void);
+                    }
+                }
+
+                for i in 0..sessions {
+                    free(*sessions_list.add(i as usize) as *mut c_void);
+                }
+                free(sessions_list as *mut c_void);
+
+                return format_user(num_user);
+            }
+        }
+
+        // utmpx
+        let mut num_user = 0;
+        setutxent();
+        let mut ut = getutxent();
+        while !ut.is_null() {
+            if ((*ut).ut_type == 7) && ((*ut).ut_user[0] != ('\0' as i8)) {
+                num_user += 1;
+            }
+            ut = getutxent();
+        }
+        endutxent();
+        format_user(num_user)
+    }
 }
 
 #[cfg(not(target_os = "windows"))]
@@ -214,9 +327,7 @@ fn memory(arg: &ArgMatches) -> String {
             "e" => (1_152_921_504_606_846_976, "EiB"),
             _ => (bytesize::MIB, "MiB"),
         },
-        None => {
-            (bytesize::MIB, "MiB")
-        }
+        None => (bytesize::MIB, "MiB"),
     };
 
     format!(