From c7b80825bc170862574d8f4e1827a59da2d07737 Mon Sep 17 00:00:00 2001
From: driphtyio <driphtyio@users.noreply.github.com>
Date: Thu, 18 Jun 2026 14:54:02 -0700
Subject: [PATCH] fix: serve zero-size files (e.g. /proc) with proper content

When stat.size === 0 (e.g. /proc virtual filesystem files),
don't limit the read stream to byte 0 and don't set
Content-Length: 0. Let the stream read until EOF and use
chunked transfer encoding.

Fixes expressjs/express#4944
---
 index.js     | 8 ++++++--
 test/send.js | 1 -
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/index.js b/index.js
index 1655053..4836893 100644
--- a/index.js
+++ b/index.js
@@ -577,10 +577,14 @@ SendStream.prototype.send = function send (path, stat) {
 
   // set read options
   opts.start = offset
-  opts.end = Math.max(offset, offset + len - 1)
+  if (len > 0) {
+    opts.end = Math.max(offset, offset + len - 1)
+  }
 
   // content-length
-  res.setHeader('Content-Length', len)
+  if (len > 0) {
+    res.setHeader('Content-Length', len)
+  }
 
   // HEAD support
   if (req.method === 'HEAD') {
diff --git a/test/send.js b/test/send.js
index b824282..2f26e12 100644
--- a/test/send.js
+++ b/test/send.js
@@ -35,7 +35,6 @@ describe('send(file).pipe(res)', function () {
   it('should stream a zero-length file', function (done) {
     request(app)
       .get('/empty.txt')
-      .expect('Content-Length', '0')
       .expect(200, '', done)
   })