From 7ca5f66fa1deec91c75868816baac0efb60eb0af Mon Sep 17 00:00:00 2001
From: mattsu <matsui.atsushi.home@gmail.com>
Date: Mon, 3 Nov 2025 21:20:42 +0900
Subject: [PATCH] feat(truncate): allow negative size values for truncation

- Enable hyphen values in size argument to support negative sizes (e.g., "-1")
- Add test case verifying truncation to empty file with negative size "-1"
---
 src/uu/truncate/src/truncate.rs |  1 +
 tests/by-util/test_truncate.rs  | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/src/uu/truncate/src/truncate.rs b/src/uu/truncate/src/truncate.rs
index a45a4ac5941..7a607cc1a45 100644
--- a/src/uu/truncate/src/truncate.rs
+++ b/src/uu/truncate/src/truncate.rs
@@ -145,6 +145,7 @@ pub fn uu_app() -> Command {
                 .long(options::SIZE)
                 .required_unless_present(options::REFERENCE)
                 .help(translate!("truncate-help-size"))
+                .allow_hyphen_values(true)
                 .value_name("SIZE"),
         )
         .arg(
diff --git a/tests/by-util/test_truncate.rs b/tests/by-util/test_truncate.rs
index 36ce92dc971..63c4442bd55 100644
--- a/tests/by-util/test_truncate.rs
+++ b/tests/by-util/test_truncate.rs
@@ -386,6 +386,17 @@ fn test_underflow_relative_size() {
     assert!(at.read_bytes(FILE1).is_empty());
 }
 
+#[test]
+fn test_negative_size_with_space() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    ucmd.args(&["-s", "-1", FILE1])
+        .succeeds()
+        .no_stdout()
+        .no_stderr();
+    assert!(at.file_exists(FILE1));
+    assert!(at.read_bytes(FILE1).is_empty());
+}
+
 #[cfg(not(windows))]
 #[test]
 fn test_fifo_error_size_only() {