grep: strip trailing (os error N) from file error messages to match GNU (#6)

src/output.rs

@@ -8,6 +8,7 @@ use crate::context_buffer::LineView;
 use std::ffi::OsStr;
 use std::io::{self, BufWriter, StdoutLock, Write};
 use std::path::Path;
+use uucore::error::strip_errno;
 
 #[cfg(target_pointer_width = "64")]
 const BUF_SIZE: usize = 128 * 1024;
@@ -195,7 +196,12 @@ impl<'a> OutputWriter<'a> {
     /// Write an IO error to stderr.
     pub fn report_io_error(&self, label: &OsStr, err: &io::Error) {
         if !self.config.no_messages && !self.config.quiet {
-            eprintln!("grep: {label}: {err}", label = label.to_string_lossy());
+            // Strip the trailing " (os error XX)" so the message matches GNU grep.
+            eprintln!(
+                "grep: {label}: {err}",
+                label = label.to_string_lossy(),
+                err = strip_errno(err)
+            );
         }
     }
 

tests/test_grep.rs

@@ -1030,6 +1030,16 @@ fn nonexistent_file_is_error() {
         .stderr_contains("does-not-exist");
 }
 
+#[test]
+fn nonexistent_file_error_has_no_os_error_suffix() {
+    // GNU prints "grep: <file>: No such file or directory" with no
+    // " (os error 2)" suffix; strip_errno keeps us byte-compatible.
+    let (_s, mut c) = ucmd();
+    c.args(&["x", "does-not-exist"])
+        .fails_with_code(2)
+        .stderr_is("grep: does-not-exist: No such file or directory\n");
+}
+
 #[test]
 fn dash_argument_means_stdin() {
     let (_s, mut c) = ucmd();