From 131e14dc6650feea26ec814e6964e9d3e94ac881 Mon Sep 17 00:00:00 2001
From: Justin Keogh <github.com@v6y.net>
Date: Sun, 1 May 2022 20:31:06 +0000
Subject: [PATCH] [utils] `locked_file`: Ignore illegal seek on `truncate`
 (#3610)

Closes #3557

Authored by: jakeogh
---
 yt_dlp/utils.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/yt_dlp/utils.py b/yt_dlp/utils.py
index 0b28b0926f..e25a112d32 100644
--- a/yt_dlp/utils.py
+++ b/yt_dlp/utils.py
@@ -2011,7 +2011,11 @@ class locked_file:
             self.f.close()
             raise
         if 'w' in self.mode:
-            self.f.truncate()
+            try:
+                self.f.truncate()
+            except OSError as e:
+                if e.errno != 29:  # Illegal seek, expected when self.f is a FIFO
+                    raise e
         return self
 
     def unlock(self):