Add error handling and some other improvements

Signed-off-by: Malhar Vora <mlvora.2010@gmail.com>

Author: vbmade2000

src/uu/kill/src/errors.rs

@@ -0,0 +1,42 @@
+// This file is part of the uutils util-linux package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use std::error::Error;
+
+use uucore::error::UError;
+
+#[derive(Debug)]
+pub enum KillError {
+    /// Unsupported platform
+    #[cfg(not(target_os = "linux"))]
+    UnsupportedPlatform,
+    OperationNotPermitted(i32),
+    NoSuchProcess(i32),
+}
+
+impl std::fmt::Display for KillError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            #[cfg(not(target_os = "linux"))]
+            Self::UnsupportedPlatform => write!(f, "kill is only supported on Linux for now"),
+            Self::OperationNotPermitted(pid) => {
+                write!(f, "bash: kill: ({pid}) - Operation not permitted")
+            }
+            Self::NoSuchProcess(pid) => write!(f, "bash: kill: ({pid}) - No such process"),
+        }
+    }
+}
+
+impl UError for KillError {
+    fn code(&self) -> i32 {
+        1
+    }
+
+    fn usage(&self) -> bool {
+        false
+    }
+}
+
+impl Error for KillError {}

src/uu/kill/src/kill.rs

@@ -4,34 +4,46 @@
 // file that was distributed with this source code.
 
 // Remove this if the tool is ported to Non-UNIX platforms.
+#![cfg_attr(not(target_os = "linux"), allow(dead_code))]
 
+mod errors;
+
+use crate::errors::KillError::{self, NoSuchProcess, OperationNotPermitted};
 use clap::{Arg, ArgAction, Command, crate_version, value_parser};
 use uucore::libc;
 use uucore::{error::UResult, format_usage, help_about, help_usage};
 
 const ABOUT: &str = help_about!("kill.md");
 const USAGE: &str = help_usage!("kill.md");
 
+#[cfg(not(target_os = "linux"))]
+fn kill(pid: i32, signal: i32) -> Result<(), KillError> {
+    Err(UnsupportedPlatform)
+}
+
+#[cfg(target_os = "linux")]
+fn kill(pid: i32, signal: i32) -> Result<(), KillError> {
+    unsafe { libc::kill(pid, signal) };
+
+    let err = std::io::Error::last_os_error().raw_os_error();
+    if let Some(err_no) = err {
+        match err_no {
+            libc::EPERM => return Err(OperationNotPermitted(pid)),
+            libc::ESRCH => return Err(NoSuchProcess(pid)),
+            _ => {}
+        }
+    }
+
+    Ok(())
+}
+
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     let matches = uu_app().try_get_matches_from(args)?;
 
     if let Some(pids) = matches.get_many::<i32>("pid") {
         for pid in pids {
-            unsafe { libc::kill(*pid, libc::SIGTERM) };
-
-            let err = std::io::Error::last_os_error().raw_os_error();
-            if let Some(err_no) = err {
-                match err_no {
-                    libc::EPERM => {
-                        eprintln!("bash: kill: ({pid}) - Operation not permitted");
-                    }
-                    libc::ESRCH => {
-                        eprintln!("bash: kill: ({pid}) - No such process");
-                    }
-                    _ => {}
-                }
-            }
+            kill(*pid, libc::SIGTERM)?;
         }
     }
 
@@ -47,7 +59,7 @@ pub fn uu_app() -> Command {
         .arg(
             Arg::new("pid")
                 .help("PID of the process to kill")
-                .required(false)
+                .required(true)
                 .action(ArgAction::Append)
                 .value_name("PID")
                 .value_parser(value_parser!(i32)),