From bbf205fc92e68ae44af83b25485c68b5d6533186 Mon Sep 17 00:00:00 2001
From: Wondr <wondr.design@gmail.com>
Date: Fri, 5 Jun 2026 03:26:12 +0100
Subject: [PATCH] grep: short-circuit max-count zero

---
 src/lib.rs         |  6 +++++-
 tests/test_grep.rs | 15 +++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index 0f2b63a..f01e11b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -20,7 +20,7 @@ use clap::{Arg, ArgAction, Command};
 use std::ffi::{OsStr, OsString};
 use std::io::{IsTerminal as _, Read};
 use std::path::Path;
-use uucore::error::{FromIo, UResult, USimpleError};
+use uucore::error::{ExitCode, FromIo, UResult, USimpleError};
 
 #[derive(Clone, Copy, PartialEq, Eq)]
 #[doc(hidden)]
@@ -399,6 +399,10 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     };
 
     let matcher = Matcher::compile(&config)?;
+    if config.max_count == Some(0) {
+        return Err(ExitCode::new(1));
+    }
+
     let writer = OutputWriter::new(&config);
     let mut searcher = Searcher::new(&config, matcher, writer);
     let mut lb = LineBuffer::new(if config.null_data { b'\0' } else { b'\n' });
diff --git a/tests/test_grep.rs b/tests/test_grep.rs
index d061918..f5f4bfd 100644
--- a/tests/test_grep.rs
+++ b/tests/test_grep.rs
@@ -278,6 +278,21 @@ fn max_count() {
         .fails_with_code(1)
         .no_stdout();
 
+    let (_s, mut c) = ucmd();
+    c.args(&["-m", "0", "a", "missing"])
+        .fails_with_code(1)
+        .no_output();
+
+    let (_s, mut c) = ucmd();
+    c.args(&["-m", "1", "a", "missing"])
+        .fails_with_code(2)
+        .stderr_contains("grep: missing:");
+
+    let (_s, mut c) = ucmd();
+    c.args(&["-m", "0", "-e", "["])
+        .fails_with_code(2)
+        .stderr_contains("invalid pattern");
+
     // -A trailing context still printed after the cutoff.
     let (_s, mut c) = ucmd();
     c.args(&["-m", "1", "-A", "2", "match"])