snice: Switch from libc to rustix (#621)

* snice: Switch from libc to rustix

Use rustix instead of libc to provide getpriority and
setpriority syscalls.

Resolves #598

* Fix build on Windows

Cargo.lock

@@ -2315,8 +2315,8 @@ name = "uu_snice"
 version = "0.0.1"
 dependencies = [
  "clap",
- "nix 0.30.1",
  "prettytable-rs",
+ "rustix",
  "sysinfo",
  "thiserror 2.0.18",
  "uu_pgrep",

Cargo.toml

@@ -68,7 +68,7 @@ prettytable-rs = "0.10.0"
 rand = { version = "0.9.0", features = ["small_rng"] }
 ratatui = "0.30.0"
 regex = "1.10.4"
-rustix = { version = "1.1.2", features = ["fs"] }
+rustix = { version = "1.1.2", features = ["fs", "process"] }
 sysinfo = "0.38.0"
 tempfile = "3.10.1"
 terminal_size = "0.4.2"

src/uu/snice/Cargo.toml

@@ -16,10 +16,10 @@ workspace = true
 [dependencies]
 uucore = { workspace = true, features = ["signals", "libc"] }
 clap = { workspace = true }
-nix = { workspace = true }
 prettytable-rs = { workspace = true }
 thiserror = { workspace = true }
 sysinfo = { workspace = true }
+rustix = { workspace = true }
 
 uu_pgrep = { path = "../pgrep" }
 

src/uu/snice/src/action.rs

@@ -108,60 +108,49 @@ impl Display for ActionResult {
 
 /// Set priority of process.
 ///
-/// But we don't know if the process of pid are exist, if [None], the process doesn't exist
-#[cfg(target_os = "linux")]
+/// But we don't know if pid is an existing process. Returns [None] if the process doesn't exist
+#[cfg(unix)]
 fn set_priority(pid: u32, prio: &Priority, take_action: bool) -> Option<ActionResult> {
-    use nix::errno::Errno;
-    use uucore::libc::{getpriority, setpriority, PRIO_PROCESS};
+    use rustix::io::Errno;
+    use rustix::process::{getpriority_process, setpriority_process, Pid};
 
-    // Very dirty.
-    let current_priority = {
-        // Clear errno
-        Errno::clear();
+    let pid = Pid::from_raw(i32::try_from(pid).ok()?);
+    let process_priority = getpriority_process(pid);
 
-        let prio = unsafe { getpriority(PRIO_PROCESS, pid) };
-        // prio == -1 might be error.
-        if prio == -1 && Errno::last() != Errno::UnknownErrno {
-            // Must clear errno.
-            Errno::clear();
-
-            // I don't know but, just considering it just caused by permission.
-            // https://manpages.debian.org/bookworm/manpages-dev/getpriority.2.en.html#ERRORS
-            return match Errno::last() {
-                Errno::ESRCH => Some(ActionResult::PermissionDenied),
-                _ => None,
-            };
+    // Expected errors:
+    // https://man7.org/linux/man-pages/man2/setpriority.2.html
+    // https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/setpriority.2.html
+    // ESRCH: no matching process
+    // EACCES: no permission to lower priority
+    // EPERM: wrong user for process
+    let current_priority = match process_priority {
+        Err(Errno::SRCH) => return None,
+        Err(_) => {
+            return Some(ActionResult::PermissionDenied);
         }
-        prio
+        Ok(priority) => priority,
     };
 
     if !take_action {
         return Some(ActionResult::Success);
     }
 
-    let prio = match prio {
+    let new_priority = match prio {
         Priority::Increase(prio) => current_priority + *prio as i32,
         Priority::Decrease(prio) => current_priority - *prio as i32,
         Priority::To(prio) => *prio as i32,
     };
 
-    // result only 0, -1
-    Errno::clear();
-    let result = unsafe { setpriority(PRIO_PROCESS, pid, prio) };
-
-    // https://manpages.debian.org/bookworm/manpages-dev/setpriority.2.en.html#ERRORS
-    if result == -1 {
-        match Errno::last() {
-            Errno::ESRCH => Some(ActionResult::PermissionDenied),
-            _ => None,
-        }
-    } else {
-        Some(ActionResult::Success)
+    let result = setpriority_process(pid, new_priority);
+    match result {
+        Err(Errno::SRCH) => None,
+        Err(_) => Some(ActionResult::PermissionDenied),
+        Ok(_) => Some(ActionResult::Success),
     }
 }
 
-// TODO: Implemented this on other platform
-#[cfg(not(target_os = "linux"))]
+// TODO: rustix doesn't support the process feature on Windows
+#[cfg(not(unix))]
 fn set_priority(_pid: u32, _prio: &Priority, _take_action: bool) -> Option<ActionResult> {
     None
 }