nice: use Command::exec() instead of libc::execvp()

Signed-off-by: Etienne Cordonnier <ecordonnier@snap.com>

Author: Ecordonnier

src/uu/nice/src/nice.rs

@@ -3,13 +3,14 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-// spell-checker:ignore (ToDO) getpriority execvp setpriority nstr PRIO cstrs ENOENT
+// spell-checker:ignore (ToDO) getpriority setpriority nstr PRIO
 
 use clap::{Arg, ArgAction, Command};
-use libc::{PRIO_PROCESS, c_char, c_int, execvp};
-use std::ffi::{CString, OsString};
-use std::io::{Error, Write};
-use std::ptr;
+use libc::PRIO_PROCESS;
+use std::ffi::OsString;
+use std::io::{Error, ErrorKind, Write};
+use std::os::unix::process::CommandExt;
+use std::process;
 
 use uucore::translate;
 use uucore::{
@@ -156,21 +157,15 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         }
     }
 
-    let cstrs: Vec<CString> = matches
-        .get_many::<String>(options::COMMAND)
-        .unwrap()
-        .map(|x| CString::new(x.as_bytes()).unwrap())
-        .collect();
+    let mut cmd_iter = matches.get_many::<String>(options::COMMAND).unwrap();
+    let cmd = cmd_iter.next().unwrap();
+    let args: Vec<&String> = cmd_iter.collect();
 
-    let mut args: Vec<*const c_char> = cstrs.iter().map(|s| s.as_ptr()).collect();
-    args.push(ptr::null::<c_char>());
-    unsafe {
-        execvp(args[0], args.as_mut_ptr());
-    }
+    let err = process::Command::new(cmd).args(args).exec();
 
-    show_error!("execvp: {}", Error::last_os_error());
+    show_error!("{}: {}", cmd, err);
 
-    let exit_code = if Error::last_os_error().raw_os_error().unwrap() as c_int == libc::ENOENT {
+    let exit_code = if err.kind() == ErrorKind::NotFound {
         127
     } else {
         126