Revert "env: use Command::exec() instead of libc::execvp()"

This reverts commit e27da7e.

Author: Ecordonnier

src/uu/env/src/env.rs

@@ -3,7 +3,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-// spell-checker:ignore (ToDO) chdir progname subcommand subcommands unsets setenv putenv spawnp SIGSEGV SIGBUS sigaction
+// spell-checker:ignore (ToDO) chdir execvp progname subcommand subcommands unsets setenv putenv spawnp SIGSEGV SIGBUS sigaction
 
 pub mod native_int_str;
 pub mod split_iterator;
@@ -21,14 +21,16 @@ use native_int_str::{
 use nix::libc;
 #[cfg(unix)]
 use nix::sys::signal::{SigHandler::SigIgn, Signal, signal};
+#[cfg(unix)]
+use nix::unistd::execvp;
 use std::borrow::Cow;
 use std::env;
+#[cfg(unix)]
+use std::ffi::CString;
 use std::ffi::{OsStr, OsString};
 use std::io::{self, Write};
 #[cfg(unix)]
 use std::os::unix::ffi::OsStrExt;
-#[cfg(unix)]
-use std::os::unix::process::CommandExt;
 
 use uucore::display::Quotable;
 use uucore::error::{ExitCode, UError, UResult, USimpleError, UUsageError};
@@ -604,16 +606,34 @@ impl EnvAppData {
 
         #[cfg(unix)]
         {
-            // Execute the program using exec, which replaces the current process.
-            let err = std::process::Command::new(&*prog)
-                .arg0(&*arg0)
-                .args(args)
-                .exec();
-
-            // exec() only returns if there was an error
-            match err.kind() {
-                io::ErrorKind::NotFound => Err(self.make_error_no_such_file_or_dir(&prog)),
-                io::ErrorKind::PermissionDenied => {
+            // Convert program name to CString.
+            let Ok(prog_cstring) = CString::new(prog.as_bytes()) else {
+                return Err(self.make_error_no_such_file_or_dir(&prog));
+            };
+
+            // Prepare arguments for execvp.
+            let mut argv = Vec::new();
+
+            // Convert arg0 to CString.
+            let Ok(arg0_cstring) = CString::new(arg0.as_bytes()) else {
+                return Err(self.make_error_no_such_file_or_dir(&prog));
+            };
+            argv.push(arg0_cstring);
+
+            // Convert remaining arguments to CString.
+            for arg in args {
+                let Ok(arg_cstring) = CString::new(arg.as_bytes()) else {
+                    return Err(self.make_error_no_such_file_or_dir(&prog));
+                };
+                argv.push(arg_cstring);
+            }
+
+            // Execute the program using execvp. this replaces the current
+            // process. The execvp function takes care of appending a NULL
+            // argument to the argument list so that we don't have to.
+            match execvp(&prog_cstring, &argv) {
+                Err(nix::errno::Errno::ENOENT) => Err(self.make_error_no_such_file_or_dir(&prog)),
+                Err(nix::errno::Errno::EACCES) => {
                     uucore::show_error!(
                         "{}",
                         translate!(
@@ -623,16 +643,19 @@ impl EnvAppData {
                     );
                     Err(126.into())
                 }
-                _ => {
+                Err(_) => {
                     uucore::show_error!(
                         "{}",
                         translate!(
                             "env-error-unknown",
-                            "error" => err
+                            "error" => "execvp failed"
                         )
                     );
                     Err(126.into())
                 }
+                Ok(_) => {
+                    unreachable!("execvp should never return on success")
+                }
             }
         }