ps: Add euid check for default output format

For instance, leaving a `sudo sleep 9999 &` running in the same
terminal shouldn't be displayed.

Clean up code a bit by utilizing current_process_info().

src/uu/ps/src/collector.rs

@@ -6,7 +6,7 @@
 use clap::ArgMatches;
 #[cfg(target_family = "unix")]
 use nix::errno::Errno;
-use std::{cell::RefCell, path::PathBuf, rc::Rc, str::FromStr};
+use std::{cell::RefCell, rc::Rc};
 use uu_pgrep::process::{ProcessInformation, Teletype};
 
 // TODO: Temporary add to this file, this function will add to uucore.
@@ -29,25 +29,18 @@ fn getsid(_pid: i32) -> Option<i32> {
     Some(0)
 }
 
-// Guessing it matches the current terminal
+// Default behavior: select processes with same terminal and same effective user ID
 pub(crate) fn basic_collector(
     proc_snapshot: &[Rc<RefCell<ProcessInformation>>],
 ) -> Vec<Rc<RefCell<ProcessInformation>>> {
     let mut result = Vec::new();
 
-    let current_tty = {
-        // SAFETY: The `libc::getpid` always return i32
-        let proc_path =
-            PathBuf::from_str(&format!("/proc/{}/", unsafe { libc::getpid() })).unwrap();
-        let current_proc_info = ProcessInformation::try_new(proc_path).unwrap();
-
-        current_proc_info.tty()
-    };
+    let mut cur = ProcessInformation::current_process_info().unwrap();
+    let tty = cur.tty();
+    let euid = cur.euid().unwrap();
 
     for proc_info in proc_snapshot {
-        let proc_ttys = proc_info.borrow().tty();
-
-        if proc_ttys == current_tty {
+        if proc_info.borrow().tty() == tty && proc_info.borrow_mut().euid().unwrap() == euid {
             result.push(proc_info.clone());
         }
     }