From 0e35fb23bfeb773527a98403818fa3c2f751ea53 Mon Sep 17 00:00:00 2001
From: arbelonson-source <269032023+arbelonson-source@users.noreply.github.com>
Date: Mon, 31 Aug 2026 09:48:03 +0300
Subject: [PATCH] csplit: accept a hyphen-leading --suffix-format value

--suffix-format's value was rejected as an unrecognized flag when
given as its own argument (csplit --suffix-format -%02d f /pat/, not
the attached -b-%02d or --suffix-format=-%02d): the Arg was missing
allow_hyphen_values, the same gap already fixed this session for
several other options (sort --parallel, nl's numeric options, ptx
--gap-size/--width, join -t). GNU's own --suffix-format accepts any
argument as the format string regardless of its first character.

AI-assisted-by: Claude Opus 5, via Claude Code
---
 src/uu/csplit/src/csplit.rs  |  1 +
 tests/by-util/test_csplit.rs | 14 ++++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/src/uu/csplit/src/csplit.rs b/src/uu/csplit/src/csplit.rs
index fe96f41534f..c4e9d9f5eed 100644
--- a/src/uu/csplit/src/csplit.rs
+++ b/src/uu/csplit/src/csplit.rs
@@ -680,6 +680,7 @@ pub fn uu_app() -> Command {
                 .short('b')
                 .long(options::SUFFIX_FORMAT)
                 .value_name("FORMAT")
+                .allow_hyphen_values(true)
                 .help(translate!("csplit-help-suffix-format")),
         )
         .arg(
diff --git a/tests/by-util/test_csplit.rs b/tests/by-util/test_csplit.rs
index ec60cfa2b9f..93985cc1bc4 100644
--- a/tests/by-util/test_csplit.rs
+++ b/tests/by-util/test_csplit.rs
@@ -1445,6 +1445,20 @@ fn precision_format() {
     }
 }
 
+#[test]
+fn suffix_format_hyphen_leading_as_separate_arg() {
+    // A hyphen-leading suffix format passed as its own argument (not
+    // attached with `-b-%02d`/`=`) must not be mistaken for a new,
+    // unrecognized flag.
+    let (at, mut ucmd) = at_and_ucmd!();
+    ucmd.args(&["numbers50.txt", "10", "--suffix-format", "-%02d"])
+        .succeeds()
+        .stdout_only("18\n123\n");
+
+    assert_eq!(at.read("xx-00"), generate(1, 10));
+    assert_eq!(at.read("xx-01"), generate(10, 51));
+}
+
 #[test]
 fn zero_precision_format() {
     let (at, mut ucmd) = at_and_ucmd!();