mkfifo: stop hardcoding "File exists" as the error message

src/uu/mkfifo/locales/en-US.ftl

@@ -8,6 +8,6 @@ mkfifo-help-context = like -Z, or if CTX is specified then set the SELinux or SM
 
 # Error messages
 mkfifo-error-invalid-mode = invalid mode: { $error }
-mkfifo-error-cannot-create-fifo = cannot create fifo { $path }: File exists
+mkfifo-error-cannot-create-fifo = cannot create fifo { $path }: { $error }
 mkfifo-error-cannot-set-permissions = cannot set permissions on { $path }: { $error }
 mkfifo-error-non-file-permission = mode must specify only file permission bits

src/uu/mkfifo/locales/fr-FR.ftl

@@ -8,6 +8,6 @@ mkfifo-help-context = comme -Z, ou si CTX est spécifié, définir le contexte d
 
 # Messages d'erreur
 mkfifo-error-invalid-mode = mode invalide : { $error }
-mkfifo-error-cannot-create-fifo = impossible de créer le fifo { $path } : Le fichier existe
+mkfifo-error-cannot-create-fifo = impossible de créer le fifo { $path } : { $error }
 mkfifo-error-cannot-set-permissions = impossible de définir les permissions sur { $path } : { $error }
 mkfifo-error-non-file-permission = le mode ne doit spécifier que des bits de permission de fichier

src/uu/mkfifo/src/mkfifo.rs

@@ -7,7 +7,7 @@ use clap::{Arg, ArgAction, Command, value_parser};
 use rustix::fs::Mode;
 use rustix::process::umask;
 use uucore::display::Quotable;
-use uucore::error::{UResult, USimpleError};
+use uucore::error::{UResult, USimpleError, strip_errno};
 use uucore::translate;
 
 use uucore::{format_usage, show};
@@ -52,10 +52,14 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         let mkfifo_result = create_fifo(f.as_str(), mode);
         umask(prev_umask);
 
-        if mkfifo_result.is_err() {
+        if let Err(e) = mkfifo_result {
             show!(USimpleError::new(
                 1,
-                translate!("mkfifo-error-cannot-create-fifo", "path" => f.quote()),
+                translate!(
+                    "mkfifo-error-cannot-create-fifo",
+                    "path" => f.quote(),
+                    "error" => strip_errno(&e)
+                ),
             ));
         } else {
             // Apply SELinux context if requested
@@ -134,19 +138,24 @@ pub fn uu_app() -> Command {
 // libc's path-based `mkfifo` there. Both rely on the caller having cleared
 // the umask so the requested mode is applied atomically (see issue #10020).
 #[cfg(not(target_vendor = "apple"))]
-fn create_fifo(path: &str, mode: u32) -> Result<(), ()> {
+fn create_fifo(path: &str, mode: u32) -> Result<(), std::io::Error> {
     use rustix::fs::{CWD, mkfifoat};
-    mkfifoat(CWD, path, Mode::from_bits_truncate(mode)).map_err(|_| ())
+    mkfifoat(CWD, path, Mode::from_bits_truncate(mode)).map_err(std::io::Error::from)
 }
 
 #[cfg(target_vendor = "apple")]
-fn create_fifo(path: &str, mode: u32) -> Result<(), ()> {
+fn create_fifo(path: &str, mode: u32) -> Result<(), std::io::Error> {
     use std::ffi::CString;
-    let c_path = CString::new(path).map_err(|_| ())?;
+    let c_path =
+        CString::new(path).map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidInput, e))?;
     // SAFETY: `c_path` is a valid NUL-terminated C string and `mode` is a
     // standard mode_t bit pattern.
     let rc = unsafe { libc::mkfifo(c_path.as_ptr(), mode as libc::mode_t) };
-    if rc == 0 { Ok(()) } else { Err(()) }
+    if rc == 0 {
+        Ok(())
+    } else {
+        Err(std::io::Error::last_os_error())
+    }
 }
 
 fn calculate_mode(mode_option: Option<&String>) -> Result<u32, String> {

tests/by-util/test_mkfifo.rs

@@ -156,9 +156,10 @@ fn test_create_fifo_permission_denied() {
     at.mkdir(no_exec_dir);
     at.set_mode(no_exec_dir, 0o644);
 
-    // We no longer attempt to modify file permission if the file was failed to be created.
-    // Therefore the error message should only contain "cannot create".
-    let err_msg = format!("mkfifo: cannot create fifo '{named_pipe}': File exists\n");
+    // The parent directory has no execute bit, so the kernel refuses to add
+    // an entry to it (EACCES). mkfifo should surface that reason instead of
+    // the old hardcoded "File exists".
+    let err_msg = format!("mkfifo: cannot create fifo '{named_pipe}': Permission denied\n");
 
     scene
         .ucmd()